Common light chain mouse

ABSTRACT

A genetically modified mouse is provided, wherein the mouse is incapable of rearranging and expressing an endogenous mouse immunoglobulin light chain variable sequence, wherein the mouse expresses only one or two human light chain variable domains encoded by human immunoglobulin sequences operably linked to the mouse kappa (κ) constant gene at the endogenous mouse κ locus, wherein the mouse expresses a reverse chimeric antibody having a light chain variable domain derived from one of only two human light chain variable region gene segments and a mouse κ constant domain, and a human heavy chain variable domain and a mouse heavy chain constant domain, from an endogenous mouse heavy chain locus. Bispecific epitope-binding proteins that are fully human are provided, comprising two different heavy chains that associate with an identical light chain that comprises a variable domain derived from one of two different human light chain variable region gene segments.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/022,759, entitled “Common Light Chain Mouse”, filed on 8 Feb. 2011,which claims the benefit under 35 USC §119(e) of U.S. ProvisionalApplication Ser. No. 61/302,282, filed 8 Feb. 2010, the disclosures ofwhich are herein incorporated by reference in their entireties.

SEQUENCE LISTING

Incorporated by reference herein in its entirety is the Sequence Listingentitled “40848_(—)0015USC1_SEQ_LIST_TEXT_FILE_(—)2013_(—)07_(—)23.txt”,created Jul. 23, 2013 size of 14.3 kilobytes.

FIELD OF INVENTION

A genetically modified mouse is provided that expresses antibodieshaving a common human variable/mouse constant light chain associatedwith diverse human variable/mouse constant heavy chains. A method formaking a human bispecific antibody from human variable region genesequences of B cells of the mouse is provided.

BACKGROUND

Antibodies typically comprise a homodimeric heavy chain component,wherein each heavy chain monomer is associated with an identical lightchain. Antibodies having a heterodimeric heavy chain component (e.g.,bispecific antibodies) are desirable as therapeutic antibodies. Butmaking bispecific antibodies having a suitable light chain componentthat can satisfactorily associate with each of the heavy chains of abispecific antibody has proved problematic.

In one approach, a light chain might be selected by surveying usagestatistics for all light chain variable domains, identifying the mostfrequently employed light chain in human antibodies, and pairing thatlight chain in vitro with the two heavy chains of differing specificity.

In another approach, a light chain might be selected by observing lightchain sequences in a phage display library (e.g., a phage displaylibrary comprising human light chain variable region sequences, e.g., ahuman ScFv library) and selecting the most commonly used light chainvariable region from the library. The light chain can then be tested onthe two different heavy chains of interest.

In another approach, a light chain might be selected by assaying a phagedisplay library of light chain variable sequences using the heavy chainvariable sequences of both heavy chains of interest as probes. A lightchain that associates with both heavy chain variable sequences might beselected as a light chain for the heavy chains.

In another approach, a candidate light chain might be aligned with theheavy chains' cognate light chains, and modifications are made in thelight chain to more closely match sequence characteristics common to thecognate light chains of both heavy chains. If the chances ofimmunogenicity need to be minimized, the modifications preferably resultin sequences that are present in known human light chain sequences, suchthat proteolytic processing is unlikely to generate a T cell epitopebased on parameters and methods known in the art for assessing thelikelihood of immunogenicity (i.e., in silico as well as wet assays).

All of the above approaches rely on in vitro methods that subsume anumber of a priori restraints, e.g., sequence identity, ability toassociate with specific pre-selected heavy chains, etc. There is a needin the art for compositions and methods that do not rely on manipulatingin vitro conditions, but that instead employ more biologically sensibleapproaches to making human epitope-binding proteins that include acommon light chain.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates a targeting strategy for replacing endogenous mouseimmunoglobulin light chain variable region gene segments with a humanVκ1-39Jκ5 gene region.

FIG. 2 illustrates a targeting strategy for replacing endogenous mouseimmunoglobulin light chain variable region gene segments with a humanVκ3-20Jκ1 gene region.

FIG. 3 illustrates a targeting strategy for replacing endogenous mouseimmunoglobulin light chain variable region gene segments with a humanVpreB/Jλ5 gene region.

SUMMARY

Genetically modified mice that express human immunoglobulin heavy andlight chain variable domains, wherein the mice have a limited lightchain variable repertoire, are provided. A biological system forgenerating a human light chain variable domain that associates andexpresses with a diverse repertoire of affinity-matured human heavychain variable domains is provided. Methods for making binding proteinscomprising immunoglobulin variable domains are provided, comprisingimmunizing mice that have a limited immunoglobulin light chainrepertoire with an antigen of interest, and employing an immunoglobulinvariable region gene sequence of the mouse in a binding protein thatspecifically binds the antigen of interest. Methods include methods formaking human immunoglobulin heavy chain variable domains suitable foruse in making multi-specific antigen-binding proteins.

Genetically engineered mice are provided that select suitableaffinity-matured human immunoglobulin heavy chain variable domainsderived from a repertoire of unrearranged human heavy chain variableregion gene segments, wherein the affinity-matured human heavy chainvariable domains associate and express with a single human light chainvariable domain derived from one human light chain variable region genesegment. Genetically engineered mice that present a choice of two humanlight chain variable region gene segments are also provided.

Genetically engineered mice are provided that express a limitedrepertoire of human light chain variable domains, or a single humanlight chain variable domain, from a limited repertoire of human lightchain variable region gene segments. The mice are genetically engineeredto include a single unrearranged human light chain variable region genesegment (or two human light chain variable region gene segments) thatrearranges to form a rearranged human light chain variable region gene(or two rearranged light chain variable region genes) that express asingle light chain (or that express either or both of two light chains).The rearranged human light chain variable domains are capable of pairingwith a plurality of affinity-matured human heavy chains selected by themice, wherein the heavy chain variable regions specifically binddifferent epitopes.

In one aspect, a genetically modified mouse is provided that comprises asingle human immunoglobulin light chain variable (VL) region genesegment that is capable of rearranging and encoding a human VL domain ofan immunoglobulin light chain. In another aspect, the mouse comprises nomore than two human VL gene segments that are capable of rearranging andencoding a human VL domain of an immunoglobulin light chain.

In one aspect, a genetically modified mouse is provided that comprises asingle rearranged (V/J) human immunoglobulin light chain variable (VL)region segment (i.e., a V/J segment) that encodes a human VL domain ofan immunoglobulin light chain. In another aspect, the mouse comprises nomore than two rearranged human VL gene segments that are capable ofencoding a human VL domain of an immunoglobulin light chain.

In one embodiment, the VL gene segment is a human Vκ1-39Jκ5 gene segmentor a human Vκ3-20Jκ1 gene segment. In one embodiment, the mouse has botha human Vκ39Jκ5 gene segment and a human Vκ3-20Jκ1 gene segment.

In one embodiment, the human VL gene segment is operably linked to ahuman or mouse leader sequence. In one embodiment, the leader sequenceis a mouse leader sequence. In a specific embodiment, the mouse leadersequence is a mouse Vκ3-7 leader sequence.

In one embodiment, the VL gene segment is operably linked to animmunoglobulin promoter sequence. In one embodiment, the promotersequence is a human promoter sequence. In a specific embodiment, thehuman immunoglobulin promoter is a Vκ3-15 promoter.

In one embodiment, the genetically modified mouse comprises a VL locusthat does not comprise an endogenous mouse VL gene segment that iscapable of rearranging to form an immunoglobulin light chain gene,wherein the VL locus comprises a single human VL gene segment that iscapable of rearranging to encode a VL region of a light chain gene. In aspecific embodiment, the human VL gene segment is a human Vκ1-39Jκ5 genesegment or a human Vκ3-20Kκ1 gene segment.

In one embodiment, the VL locus comprises a leader sequence flanked 5′(with respect to transcriptional direction of the VL gene segment) witha human immunoglobulin promoter and flanked 3′ with a human VL genesegment that rearranges and encodes VL domain of a reverse chimericlight chain comprising an endogenous mouse light chain constant region(CL). In a specific embodiment, the VL gene segment is at the mousekappa (κ) VL locus, and the mouse CL is a mouse κ CL.

In one embodiment, the mouse comprises a nonfunctional lambda (λ)immunoglobulin light chain locus. In a specific embodiment, the λ locuscomprises a deletion of one or more sequences of the locus, wherein theone or more deletions renders the λ locus incapable of rearranging toform a light chain gene. In another embodiment all or substantially allof the VL gene segments of the λ locus are deleted.

In one embodiment, the VL locus of the modified mouse is a κ locus, andthe κ locus comprises a mouse κ intronic enhancer, a mouse κ 3′enhancer, or both an intronic enhancer and a 3′ enhancer.

In one embodiment, mouse makes a light chain that comprises asomatically mutated VL domain derived from a human VL gene segment. Inone embodiment, the light chain comprises a somatically mutated VLdomain derived from a human VL gene segment, and a mouse κ CL region. Inone embodiment, the mouse does not express a λ light chain.

In one embodiment, the genetically modified mouse is capable ofsomatically hypermutating the human VL region sequence. In a specificembodiment, the mouse comprises a cell that comprises a rearrangedimmunoglobulin light chain gene derived from the human VL gene segmentthat is capable of rearranging and encoding a VL domain, and therearranged immunoglobulin light chain gene comprises a somaticallymutated VL domain.

In one embodiment, the mouse comprises a cell that expresses a lightchain comprising a somatically mutated human VL domain linked to a mouseκ CL, wherein the light chain associates with a heavy chain comprising asomatically mutated VH domain derived from a human VH gene segment andwherein the heavy chain comprises a mouse heavy chain constant region(CH).

In one embodiment, the mouse comprises a replacement of endogenous mouseVH gene segments with one or more human VH gene segments, wherein thehuman VH gene segments are operably linked to a mouse CH region gene,such that the mouse rearranges the human VH gene segments and expressesa reverse chimeric immunoglobulin heavy chain that comprises a human VHdomain and a mouse CH. In one embodiment, 90-100% of unrearranged mouseVH gene segments are replaced with at least one unrearranged human VHgene segment. In a specific embodiment, all or substantially all of theendogenous mouse VH gene segments are replaced with at least oneunrearranged human VH gene segment. In one embodiment, the replacementis with at least 19, at least 39, or at least 80 or 81 unrearrangedhuman VH gene segments. In one embodiment, the replacement is with atleast 12 functional unrearranged human VH gene segments, at least 25functional unrearranged human VH gene segments, or at least 43functional unrearranged human VH gene segments. In one embodiment, themouse comprises a replacement of all mouse D and J segments with atleast one unrearranged human D segment and at least one unrearrangedhuman J segment. In one embodiment, the at least one unrearranged humanD segment is selected from D1-7, D1-26, D3-3, D3-10, D3-16, D3-22, D5-5,D5-12, D6-6, D6-13, D7-27, and a combination thereof. In one embodiment,the at least one unrearranged human J segment is selected from J1, J3,J4, J5, J6, and a combination thereof. In a specific embodiment, the oneor more human VH gene segment is selected from a 1-2, 1-8, 1-24, 2-5,3-7, 3-9, 3-11, 3-13, 3-15, 3-20, 3-23, 3-30, 3-33, 3-48, 4-31, 4-39,4-59, 5-51, a 6-1 human VH gene segment, and a combination thereof.

In one embodiment, the mouse comprises a B cell that expresses a bindingprotein that specifically binds an antigen of interest, wherein thebinding protein comprises a light chain derived from a human Vκ1-39/Jκ5rearrangement or a human Vκ3-20/Jκ1 rearrangement, and wherein the cellcomprises a rearranged immunoglobulin heavy chain gene derived from arearrangement of human gene segments selected from a VH2-5, VH3-23,VH3-30, VH 4-39, VH4-59, and VH5-51 gene segment. In one embodiment, theone or more human VH gene segments are rearranged with a human heavychain J gene segment selected from J1, J3, J4, J5, and J6. In oneembodiment, the one or more human VH and J gene segments are rearrangedwith a human D gene segment selected from D1-7, D1-26, D3-3, D3-10,D3-16, D3-22, D5-5, D5-12, D6-6, D6-13, and D7-27. In a specificembodiment, the light chain gene has 1, 2, 3, 4, or 5 or more somatichypermutations.

In one embodiment, the mouse comprises a B cell that comprises arearranged immunoglobulin heavy chain variable region gene sequencecomprising a VH, JH, and DH gene segment selected from VH 2-5+JH1+D6-6,VH3-23+JH4+D3, VH3-23+JH4+D3-10, VH3-30+JH1+D6-6, VH3-30+JH3+D6-6,VH3-30+JH4+D1-7, VH3-30+JH4+D5-12, VH3-30+JH4+D6-13, VH3-30+JH4+D6-6,VH3-30+JH4+D7-27, VH3-30+JH5+D3-22, VH3-30+JH5+D6-6, VH3-30+JH5+D7-27,VH4-39+JH3+D1-26, VH4-59+JH3+D3-16, VH4-59+JH3+D3-22, VH4-59+JH4+D3-16,VH5-51+JH3+D5-5, VH5-51+JH5+D6-13, and VH5-51+JH6+D3-16. In a specificembodiment, the B cell expresses a binding protein comprising a humanimmunoglobulin heavy chain variable region fused with a mouse heavychain constant region, and a human immunoglobulin light chain variableregion fused with a mouse light chain constant region.

In one embodiment, the human VL gene segment is a human Vκ1-39Jκ5 genesegment, and the mouse expresses a reverse chimeric light chaincomprising (i) a VL domain derived from the human VL gene segment and(ii) a mouse CL; wherein the light chain is associated with a reversechimeric heavy chain comprising (i) a mouse CH and (ii) a somaticallymutated human VH domain derived from a human VH gene segment selectedfrom a 1-2, 1-8, 1-24, 2-5, 3-7, 3-9, 3-11, 3-13, 3-15, 3-20, 3-23,3-30, 3-33, 3-48, 4-31, 4-39, 4-59, 5-51, and 6-1 human VH gene segment,and a combination thereof. In one embodiment, the mouse expresses alight chain that is somatically mutated. In one embodiment the CL is amouse κ CL.

In one embodiment, the human VL gene segment is a human Vκ3-20Jκ1 genesegment, and the mouse expresses a reverse chimeric light chaincomprising (i) a VL domain derived from the human VL gene segment, and(ii) a mouse CL; wherein the light chain is associated with a reversechimeric heavy chain comprising (i) a mouse CH, and (ii) a somaticallymutated human VH derived from a human VH gene segment selected from a1-2, 2-5, 3-7, 3-9, 3-11, 3-20, 3-23, 3-30, 3-33, 4-59, and 5-51 humanVH gene segment, and a combination thereof. In one embodiment, the mouseexpresses a light chain that is somatically mutated. In one embodimentthe CL is a mouse κ CL.

In one embodiment, the mouse comprises both a human Vκ1-39Jκ5 genesegment and a human Vκ3-20Jκ1 gene segment, and the mouse expresses areverse chimeric light chain comprising (i) a VL domain derived from ahuman Vκ1-39Jκ5 gene segment or a human Vκ3-20Jκ1 gene segment, and (ii)a mouse CL; wherein the light chain is associated with a reversechimeric heavy chain comprising (i) a mouse CH, and (ii) a somaticallymutated human VH derived from a human VH gene segment selected from a1-2, 1-8, 1-24, 2-5, 3-7, 3-9, 3-11, 3-13, 3-15, 3-20, 3-23, 3-30, 3-33,3-48, 4-31, 4-39, 4-59, 5-51, a 6-1 human VH gene segment, and acombination thereof. In one embodiment, the mouse expresses a lightchain that is somatically mutated. In one embodiment the CL is a mouse κCL.

In one embodiment, 90-100% of the endogenous unrearranged mouse VH genesegments are replaced with at least one unrearranged human VH genesegment. In a specific embodiment, all or substantially all of theendogenous unrearranged mouse VH gene segments are replaced with atleast one unrearranged human VH gene segment. In one embodiment, thereplacement is with at least 18, at least 39, at least 80, or 81unrearranged human VH gene segments. In one embodiment, the replacementis with at least 12 functional unrearranged human VH gene segments, atleast 25 functional unrearranged human VH gene segments, or at least 43unrearranged human VH gene segments.

In one embodiment, the genetically modified mouse is a C57BL strain, ina specific embodiment selected from C57BL/A, C57BL/An, C57BL/GrFa,C57BL/KaLwN, C57BL/6, C57BL/6J, C57BL/6ByJ, C57BL/6NJ, C57BL/10,C57BL/10ScSn, C57BL/10Cr, C57BL/Ola. In a specific embodiment, thegenetically modified mouse is a mix of an aforementioned 129 strain andan aforementioned C57BL/6 strain. In another specific embodiment, themouse is a mix of aforementioned 129 strains, or a mix of aforementionedBL/6 strains. In a specific embodiment, the 129 strain of the mix is a129S6 (129/SvEvTac) strain.

In one embodiment, the mouse expresses a reverse chimeric antibodycomprising a light chain that comprises a mouse κ CL and a somaticallymutated human VL domain derived from a human Vκ1-39Jκ5 gene segment or ahuman Vκ3-20Jκ1 gene segment, and a heavy chain that comprises a mouseCH and a somatically mutated human VH domain derived from a human VHgene segment selected from a 1-2, 1-8, 1-24, 2-5, 3-7, 3-9, 3-11, 3-13,3-15, 3-20, 3-23, 3-30, 3-33, 3-48, 4-31, 4-39, 4-59, 5-51, and a 6-1human VH gene segment, wherein the mouse does not express a fully mouseantibody and does not express a fully human antibody. In one embodimentthe mouse comprises a κ light chain locus that comprises a replacementof endogenous mouse κ VL gene segments with the human Vκ1-39Jκ5 genesegment or the human Vκ3-20Jκ1 gene segment, and comprises a replacementof all or substantially all endogenous mouse VH gene segments with acomplete or substantially complete repertoire of human VH gene segments.

In one aspect, a mouse cell is provided that is isolated from a mouse asdescribed herein. In one embodiment, the cell is an ES cell. In oneembodiment, the cell is a lymphocyte. In one embodiment, the lymphocyteis a B cell. In one embodiment, the B cell expresses a chimeric heavychain comprising a variable domain derived from a human gene segment;and a light chain derived from a rearranged human Vκ1-39/J segment,rearranged human Vκ3-20/J segment, or a combination thereof; wherein theheavy chain variable domain is fused to a mouse constant region and thelight chain variable domain is fused to a mouse or a human constantregion.

In one aspect, a hybridoma is provided, wherein the hybridoma is madewith a B cell of a mouse as described herein. In a specific embodiment,the B cell is from a mouse as described herein that has been immunizedwith an immunogen comprising an epitope of interest, and the B cellexpresses a binding protein that binds the epitope of interest, thebinding protein has a somatically mutated human VH domain and a mouseCH, and has a human VL domain derived from a human Vκ1-39Jκ5 or a humanVκ3-20Jκ1 gene segment and a mouse CL.

In one aspect, a mouse embryo is provided, wherein the embryo comprisesa donor ES cell that is derived from a mouse as described herein.

In one aspect, a targeting vector is provided, comprising, from 5′ to 3′in transcriptional direction with reference to the sequences of the 5′and 3′ mouse homology arms of the vector, a 5′ mouse homology arm, ahuman or mouse immunoglobulin promoter, a human or mouse leadersequence, and a human LCVR gene segment selected from a human Vκ1-39Jκ5or a human Vκ3-20Jκ1 gene segment, and a 3′ mouse homology arm. In oneembodiment, the 5′ and 3′ homology arms target the vector to a sequence5′ with respect to an enhancer sequence that is present 5′ and proximalto the mouse κ constant region gene. In one embodiment, the promoter isa human immunoglobulin variable region gene segment promoter. In aspecific embodiment, the promoter is a human Vκ3-15 promoter. In oneembodiment, the leader sequence is a mouse leader sequence. In aspecific embodiment, the mouse leader sequence is a mouse Vκ3-7 leadersequence.

In one aspect, a targeting vector is provided as described above, but inplace of the 5′ mouse homology arm the human or mouse promoter isflanked 5′ with a site-specific recombinase recognition site (SRRS), andin place of the 3′ mouse homology arm the human LCVR gene segment isflanked 3′ with an SRRS.

In one aspect, a reverse chimeric antibody made by a mouse as describedherein, wherein the reverse chimeric antibody comprises a light chaincomprising a mouse CL and a human VL, and a heavy chain comprising ahuman VH and a mouse CH.

In one aspect, a method for making an antibody is provided, comprisingexpressing in a single cell (a) a first VH gene sequence of an immunizedmouse as described herein fused with a human CH gene sequence; (b) a VLgene sequence of an immunized mouse as described herein fused with ahuman CL gene sequence; and, (c) maintaining the cell under conditionssufficient to express a fully human antibody, and isolating theantibody. In one embodiment, the cell comprises a second VH genesequence of a second immunized mouse as described herein fused with ahuman CH gene sequence, the first VH gene sequence encodes a VH domainthat recognizes a first epitope, and the second VH gene sequence encodesa VH domain that recognizes a second epitope, wherein the first epitopeand the second epitope are not identical.

In one aspect, a method for making an epitope-binding protein isprovided, comprising exposing a mouse as described herein with animmunogen that comprises an epitope of interest, maintaining the mouseunder conditions sufficient for the mouse to generate an immunoglobulinmolecule that specifically binds the epitope of interest, and isolatingthe immunoglobulin molecule that specifically binds the epitope ofinterest; wherein the epitope-binding protein comprises a heavy chainthat comprises a somatically mutated human VH and a mouse CH, associatedwith a light chain comprising a mouse CL and a human VL derived from ahuman Vκ1-39 Jκ5 or a human Vκ3-20 Jκ1 gene segment.

In one aspect, a cell that expresses an epitope-binding protein isprovided, wherein the cell comprises: (a) a human VL nucleotide sequenceencoding a human VL domain derived from a human Vκ1-39Jκ5 or a humanVκ3-20Jκ1 gene segment, wherein the human VL nucleotide sequence isfused (directly or through a linker) to a human immunoglobulin lightchain constant domain cDNA sequence (e.g., a human κ constant domain DNAsequence); and, (b) a first human VH nucleotide sequence encoding ahuman VH domain derived from a first human VH nucleotide sequence,wherein the first human VH nucleotide sequence is fused (directly orthrough a linker) to a human immunoglobulin heavy chain constant domaincDNA sequence; wherein the epitope-binding protein recognizes a firstepitope. In one embodiment, the epitope-binding protein binds the firstepitope with a dissociation constant of lower than 10⁻⁶ M, lower than10⁻⁸M, lower than 10⁻⁶ M, lower than 10⁻¹⁰ M, lower than 10⁻¹¹ M, orlower than 10⁻¹² M.

In one embodiment, the cell comprises a second human VH nucleotidesequence encoding a second human VH domain, wherein the second human VHsequence is fused (directly or through a linker) to a humanimmunoglobulin heavy chain constant domain cDNA sequence, and whereinthe second human VH domain does not specifically recognize the firstepitope (e.g., displays a dissociation constant of, e.g., 10⁻⁶ M, 10⁻⁵M, 10⁻⁴ M, or higher), and wherein the epitope-binding proteinrecognizes the first epitope and the second epitope, and wherein thefirst and the second immunoglobulin heavy chains each associate with anidentical light chain of (a).

In one embodiment, the second VH domain binds the second epitope with adissociation constant that is lower than 10⁻⁶ M, lower than 10⁻⁷M, lowerthan 10⁻⁸ M, lower than 10⁻⁹ M, lower than 10⁻¹⁰ M, lower than 10⁻¹¹ M,or lower than 10⁻¹² M.

In one embodiment, the epitope-binding protein comprises a firstimmunoglobulin heavy chain and a second immunoglobulin heavy chain, eachassociated with an identical light chain derived from a human VL genesegment selected from a human Vκ1-39Jκ5 or a human Vκ3-20Jκ1 genesegment, wherein the first immunoglobulin heavy chain binds a firstepitope with a dissociation constant in the nanomolar to picomolarrange, the second immunoglobulin heavy chain binds a second epitope witha dissociation constant in the nanomolar to picomolar range, the firstepitope and the second epitope are not identical, the firstimmunoglobulin heavy chain does not bind the second epitope or binds thesecond epitope with a dissociation constant weaker than the micromolarrange (e.g., the millimolar range), the second immunoglobulin heavychain does not bind the first epitope or binds the first epitope with adissociation constant weaker than the micromolar range (e.g., themillimolar range), and one or more of the VL, the VH of the firstimmunoglobulin heavy chain, and the VH of the second immunoglobulinheavy chain, are somatically mutated.

In one embodiment, the first immunoglobulin heavy chain comprises aprotein A-binding residue, and the second immunoglobulin heavy chainlacks the protein A-binding residue.

In one embodiment, the cell is selected from CHO, COS, 293, HeLa, and aretinal cell expressing a viral nucleic acid sequence (e.g., a PERC.6™cell).

In one aspect, a reverse chimeric antibody is provided, comprising ahuman VH and a mouse heavy chain constant domain, a human VL and a mouselight chain constant domain, wherein the antibody is made by a processthat comprises immunizing a mouse as described herein with an immunogencomprising an epitope, and the antibody specifically binds the epitopeof the immunogen with which the mouse was immunized. In one embodiment,the VL domain is somatically mutated. In one embodiment the VH domain issomatically mutated. In one embodiment, both the VL domain and the VHdomain are somatically mutated. In one embodiment, the VL is linked to amouse κ constant domain.

In one aspect, a mouse is provided, comprising human heavy chainvariable gene segments replacing all or substantially all mouse heavychain variable gene segments at the endogenous mouse locus; no more thanone or two human light chain variable gene segments selected from arearranged Vκ1-39/J and a rearranged Vκ3-20/J segment or a combinationthereof, replacing all mouse light chain variable gene segments; whereinthe human heavy chain variable gene segments are linked to a mouseconstant gene, and the human light chain variable gene segment(s) islinked to a human or mouse constant gene.

In one aspect, a mouse ES cell comprising a replacement of all orsubstantially all mouse heavy chain variable gene segments with humanheavy chain variable gene segments, and no more than one or tworearranged human light chain V/J segments, wherein the human heavy chainvariable gene segments are linked to a mouse immunoglobulin heavy chainconstant gene, and the human light chain V/J segments are linked to amouse or human immunoglobulin light chain constant gene. In a specificembodiment, the light chain constant gene is a mouse constant gene.

In one aspect, an antigen-binding protein made by a mouse as describedherein is provided. In a specific embodiment, the antigen-bindingprotein comprises a human immunoglobulin heavy chain variable regionfused with a mouse constant region, and a human immunoglobulin lightchain variable region derived from a Vκ1-39 gene segment or a Vκ3-20gene segment, wherein the light chain constant region is a mouseconstant region.

In one aspect, a fully human antigen-binding protein made from animmunoglobulin variable region gene sequence from a mouse as describedherein is provided, wherein the antigen-binding protein comprises afully human heavy chain comprising a human variable region derived froma sequence of a mouse as described herein, and a fully human light chaincomprising a Vκ1-39 or a Vκ3-20 variable region. In one embodiment, thelight chain variable region comprises one to five somatic mutations. Inone embodiment, the light chain variable region is a cognate light chainvariable region that is paired in a B cell of the mouse with the heavychain variable region.

In one embodiment, the fully human antigen-binding protein comprises afirst heavy chain and a second heavy chain, wherein the first heavychain and the second heavy chain comprise non-identical variable regionsindependently derived from a mouse as described herein, and wherein eachof the first and second heavy chains express from a host cell associatedwith a human light chain derived from a Vκ1-39 gene segment or a Vκ3-20gene segment. In one embodiment, the first heavy chain comprises a firstheavy chain variable region that specifically binds a first epitope of afirst antigen, and the second heavy chain comprises a second heavy chainvariable region that specifically binds a second epitope of a secondantigen. In a specific embodiment, the first antigen and the secondantigen are different. In a specific embodiment, the first antigen andthe second antigen are the same, and the first epitope and the secondepitope are not identical; in a specific embodiment, binding of thefirst epitope by a first molecule of the binding protein does not blockbinding of the second epitope by a second molecule of the bindingprotein.

In one aspect, a fully human binding protein derived from a humanimmunoglobulin sequence of a mouse as described herein comprises a firstimmunoglobulin heavy chain and a second immunoglobulin heavy chain,wherein the first immunoglobulin heavy chain comprises a first variableregion that is not identical to a variable region of the secondimmunoglobulin heavy chain, and wherein the first immunoglobulin heavychain comprises a wild-type protein A binding determinant, and thesecond heavy chain lacks a wild-type protein A binding determinant. Inone embodiment, the first immunoglobulin heavy chain binds protein Aunder isolation conditions, and the second immunoglobulin heavy chaindoes not bind protein A or binds protein A at least 10-fold, ahundred-fold, or a thousand-fold weaker than the first immunoglobulinheavy chain binds protein A under isolation conditions. In a specificembodiment, the first and the second heavy chains are IgG1 isotypes,wherein the second heavy chain comprises a modification selected from95R (EU 435R), 96F (EU 436F), and a combination thereof, and wherein thefirst heavy chain lacks such modification.

In one aspect, a method for making a bispecific antigen-binding proteinis provided, comprising exposing a first mouse as described herein to afirst antigen of interest that comprises a first epitope, exposing asecond mouse as described herein to a second antigen of interest thatcomprises a second epitope, allowing the first and the second mouse toeach mount immune responses to the antigens of interest, identifying inthe first mouse a first human heavy chain variable region that binds thefirst epitope of the first antigen of interest, identifying in thesecond mouse a second human heavy chain variable region that binds thesecond epitope of the second antigen of interest, making a first fullyhuman heavy chain gene that encodes a first heavy chain that binds thefirst epitope of the first antigen of interest, making a second fullyhuman heavy chain gene that encodes a second heavy chain that binds thesecond epitope of the second antigen of interest, expressing the firstheavy chain and the second heavy chain in a cell that expresses a singlefully human light chain derived from a human Vκ1-39 or a human Vκ3-20gene segment to form a bispecific antigen-binding protein, and isolatingthe bispecific antigen-binding protein.

In one embodiment, the first antigen and the second antigen are notidentical.

In one embodiment, the first antigen and the second antigen areidentical, and the first epitope and the second epitope are notidentical. In one embodiment, binding of the first heavy chain variableregion to the first epitope does not block binding of the second heavychain variable region to the second epitope.

In one embodiment, the first antigen is selected from a soluble antigenand a cell surface antigen (e.g., a tumor antigen), and the secondantigen comprises a cell surface receptor. In a specific embodiment, thecell surface receptor is an immunoglobulin receptor. In a specificembodiment, the immunoglobulin receptor is an Fc receptor. In oneembodiment, the first antigen and the second antigen are the same cellsurface receptor, and binding of the first heavy chain to the firstepitope does not block binding of the second heavy chain to the secondepitope.

In one embodiment, the light chain variable domain of the light chaincomprises 2 to 5 somatic mutations. In one embodiment, the light chainvariable domain is a somatically mutated cognate light chain expressedin a B cell of the first or the second immunized mouse with either thefirst or the second heavy chain variable domain.

In one embodiment, the first fully human heavy chain bears an amino acidmodification that reduces its affinity to protein A, and he second fullyhuman heavy chain does not comprise a modification that reduces itsaffinity to protein A.

In one aspect, an antibody or a bispecific antibody comprising a humanheavy chain variable domain made in accordance with the invention isprovided. In another aspect, use of a mouse as described herein to makea fully human antibody or a fully human bispecific antibody is provided.

Any of the embodiments and aspects described herein can be used inconjunction with one another, unless otherwise indicated or apparentfrom the context. Other embodiments will become apparent to thoseskilled in the art from a review of the ensuing description.

DETAILED DESCRIPTION

This invention is not limited to particular methods, and experimentalconditions described, as such methods and conditions may vary. It isalso to be understood that the terminology used herein is for thepurpose of describing particular embodiments only, and is not intendedto be limiting, since the scope of the present invention is defined bythe claims.

Unless defined otherwise, all terms and phrases used herein include themeanings that the terms and phrases have attained in the art, unless thecontrary is clearly indicated or clearly apparent from the context inwhich the term or phrase is used. Although any methods and materialssimilar or equivalent to those described herein can be used in thepractice or testing of the present invention, particular methods andmaterials are now described. All publications mentioned are herebyincorporated by reference.

The term “antibody”, as used herein, includes immunoglobulin moleculescomprising four polypeptide chains, two heavy (H) chains and two light(L) chains inter-connected by disulfide bonds. Each heavy chaincomprises a heavy chain variable (VH) region and a heavy chain constantregion (CH). The heavy chain constant region comprises three domains,CH1, CH2 and CH3. Each light chain comprises a light chain variable (VL)region and a light chain constant region (CL). The VH and VL regions canbe further subdivided into regions of hypervariability, termedcomplementarity determining regions (CDR), interspersed with regionsthat are more conserved, termed framework regions (FR). Each VH and VLcomprises three CDRs and four FRs, arranged from amino-terminus tocarboxy-terminus in the following order: FR1, CDR1, FR2, CDR2, FR3,CDR3, FR4 (heavy chain CDRs may be abbreviated as HCDR1, HCDR2 andHCDR3; light chain CDRs may be abbreviated as LCDR1, LCDR2 and LCDR3.The term “high affinity” antibody refers to an antibody that has a K_(D)with respect to its target epitope about of 10⁻⁹ M or lower (e.g., about1×10⁻⁹ M, 1×10⁻¹⁰ M, 1×10⁻¹¹ M, or about 1×10⁻¹² M). In one embodiment,K_(D) is measured by surface plasmon resonance, e.g., BIACORE™; inanother embodiment, K_(D) is measured by ELISA.

The phrase “bispecific antibody” includes an antibody capable ofselectively binding two or more epitopes. Bispecific antibodiesgenerally comprise two nonidentical heavy chains, with each heavy chainspecifically binding a different epitope—either on two differentmolecules (e.g., different epitopes on two different immunogens) or onthe same molecule (e.g., different epitopes on the same immunogen). If abispecific antibody is capable of selectively binding two differentepitopes (a first epitope and a second epitope), the affinity of thefirst heavy chain for the first epitope will generally be at least oneto two or three or four or more orders of magnitude lower than theaffinity of the first heavy chain for the second epitope, and viceversa. Epitopes specifically bound by the bispecific antibody can be onthe same or a different target (e.g., on the same or a differentprotein). Bispecific antibodies can be made, for example, by combiningheavy chains that recognize different epitopes of the same immunogen.For example, nucleic acid sequences encoding heavy chain variablesequences that recognize different epitopes of the same immunogen can befused to nucleic acid sequences encoding the same or different heavychain constant regions, and such sequences can be expressed in a cellthat expresses an immunoglobulin light chain. A typical bispecificantibody has two heavy chains each having three heavy chain CDRs,followed by (N-terminal to C-terminal) a CH1 domain, a hinge, a CH2domain, and a CH3 domain, and an immunoglobulin light chain that eitherdoes not confer epitope-binding specificity but that can associate witheach heavy chain, or that can associate with each heavy chain and thatcan bind one or more of the epitopes bound by the heavy chainepitope-binding regions, or that can associate with each heavy chain andenable binding or one or both of the heavy chains to one or bothepitopes.

The term “cell” includes any cell that is suitable for expressing arecombinant nucleic acid sequence. Cells include those of prokaryotesand eukaryotes (single-cell or multiple-cell), bacterial cells (e.g.,strains of E. coli, Bacillus spp., Streptomyces spp., etc.),mycobacteria cells, fungal cells, yeast cells (e.g., S. cerevisiae, S.pombe, P. pastoris, P. methanolica, etc.), plant cells, insect cells(e.g., SF-9, SF-21, baculovirus-infected insect cells, Trichoplusia ni,etc.), non-human animal cells, human cells, or cell fusions such as, forexample, hybridomas or quadromas. In some embodiments, the cell is ahuman, monkey, ape, hamster, rat, or mouse cell. In some embodiments,the cell is eukaryotic and is selected from the following cells: CHO(e.g., CHO K1, DXB-11 CHO, Veggie-CHO), COS (e.g., COS-7), retinal cell,Vero, CV1, kidney (e.g., HEK293, 293 EBNA, MSR 293, MDCK, HaK, BHK),HeLa, HepG2, WI38, MRC 5, Colo205, HB 8065, HL-60, (e.g., BHK21),Jurkat, Daudi, A431 (epidermal), CV-1, U937, 3T3, L cell, C127 cell,SP2/0, NS-0, MMT 060562, Sertoli cell, BRL 3A cell, HT1080 cell, myelomacell, tumor cell, and a cell line derived from an aforementioned cell.In some embodiments, the cell comprises one or more viral genes, e.g., aretinal cell that expresses a viral gene (e.g., a PER.C6™ cell).

The phrase “complementarity determining region,” or the term “CDR,”includes an amino acid sequence encoded by a nucleic acid sequence of anorganism's immunoglobulin genes that normally (i.e., in a wild-typeanimal) appears between two framework regions in a variable region of alight or a heavy chain of an immunoglobulin molecule (e.g., an antibodyor a T cell receptor). A CDR can be encoded by, for example, a germlinesequence or a rearranged or unrearranged sequence, and, for example, bya naive or a mature B cell or a T cell. A CDR can be somatically mutated(e.g., vary from a sequence encoded in an animal's germline), humanized,and/or modified with amino acid substitutions, additions, or deletions.In some circumstances (e.g., for a CDR3), CDRs can be encoded by two ormore sequences (e.g., germline sequences) that are not contiguous (e.g.,in an unrearranged nucleic acid sequence) but are contiguous in a B cellnucleic acid sequence, e.g., as the result of splicing or connecting thesequences (e.g., V-D-J recombination to form a heavy chain CDR3).

The term “conservative,” when used to describe a conservative amino acidsubstitution, includes substitution of an amino acid residue by anotheramino acid residue having a side chain R group with similar chemicalproperties (e.g., charge or hydrophobicity). In general, a conservativeamino acid substitution will not substantially change the functionalproperties of interest of a protein, for example, the ability of avariable region to specifically bind a target epitope with a desiredaffinity. Examples of groups of amino acids that have side chains withsimilar chemical properties include aliphatic side chains such asglycine, alanine, valine, leucine, and isoleucine; aliphatic-hydroxylside chains such as serine and threonine; amide-containing side chainssuch as asparagine and glutamine; aromatic side chains such asphenylalanine, tyrosine, and tryptophan; basic side chains such aslysine, arginine, and histidine; acidic side chains such as asparticacid and glutamic acid; and, sulfur-containing side chains such ascysteine and methionine. Conservative amino acids substitution groupsinclude, for example, valine/leucine/isoleucine, phenylalanine/tyrosine,lysine/arginine, alanine/valine, glutamate/aspartate, andasparagine/glutamine. In some embodiments, a conservative amino acidsubstitution can be substitution of any native residue in a protein withalanine, as used in, for example, alanine scanning mutagenesis. In someembodiments, a conservative substitution is made that has a positivevalue in the PAM250 log-likelihood matrix disclosed in Gonnet et al.(1992) Exhaustive Matching of the Entire Protein Sequence Database,Science 256:1443-45, hereby incorporated by reference. In someembodiments, the substitution is a moderately conservative substitutionwherein the substitution has a nonnegative value in the PAM250log-likelihood matrix.

In some embodiments, residue positions in an immunoglobulin light chainor heavy chain differ by one or more conservative amino acidsubstitutions. In some embodiments, residue positions in animmunoglobulin light chain or functional fragment thereof (e.g., afragment that allows expression and secretion from, e.g., a B cell) arenot identical to a light chain whose amino acid sequence is listedherein, but differs by one or more conservative amino acidsubstitutions.

The phrase “epitope-binding protein” includes a protein having at leastone CDR and that is capable of selectively recognizing an epitope, e.g.,is capable of binding an epitope with a K_(D) that is at about onemicromolar or lower (e.g., a K_(D) that is about 1×10⁻⁶ M, 1×10⁻⁷ M,1×10⁻⁹ M, 1×10⁻⁹ M, 1×10⁻¹⁰ M, 1×10⁻¹¹ M, or about 1×10⁻¹² M).Therapeutic epitope-binding proteins (e.g., therapeutic antibodies)frequently require a K_(D) that is in the nanomolar or the picomolarrange.

The phrase “functional fragment” includes fragments of epitope-bindingproteins that can be expressed, secreted, and specifically bind to anepitope with a K_(D) in the micromolar, nanomolar, or picomolar range.Specific recognition includes having a K_(D) that is at least in themicromolar range, the nanomolar range, or the picomolar range.

The term “germline” includes reference to an immunoglobulin nucleic acidsequence in a non-somatically mutated cell, e.g., a non-somaticallymutated B cell or pre-B cell or hematopoietic cell.

The phrase “heavy chain,” or “immunoglobulin heavy chain” includes animmunoglobulin heavy chain constant region sequence from any organism.Heavy chain variable domains include three heavy chain CDRs and four FRregions, unless otherwise specified. Fragments of heavy chains includeCDRs, CDRs and FRs, and combinations thereof. A typical heavy chain has,following the variable domain (from N-terminal to C-terminal), a CH1domain, a hinge, a CH2 domain, and a CH3 domain. A functional fragmentof a heavy chain includes a fragment that is capable of specificallyrecognizing an epitope (e.g., recognizing the epitope with a K_(D) inthe micromolar, nanomolar, or picomolar range), that is capable ofexpressing and secreting from a cell, and that comprises at least oneCDR.

The term “identity” when used in connection with sequence, includesidentity as determined by a number of different algorithms known in theart that can be used to measure nucleotide and/or amino acid sequenceidentity. In some embodiments described herein, identities aredetermined using a ClustalW v. 1.83 (slow) alignment employing an opengap penalty of 10.0, an extend gap penalty of 0.1, and using a Gonnetsimilarity matrix (MacVector™ 10.0.2, MacVector Inc., 2008). The lengthof the sequences compared with respect to identity of sequences willdepend upon the particular sequences, but in the case of a light chainconstant domain, the length should contain sequence of sufficient lengthto fold into a light chain constant domain that is capable ofself-association to form a canonical light chain constant domain, e.g.,capable of forming two beta sheets comprising beta strands and capableof interacting with at least one CH1 domain of a human or a mouse. Inthe case of a CH1 domain, the length of sequence should contain sequenceof sufficient length to fold into a CH1 domain that is capable offorming two beta sheets comprising beta strands and capable ofinteracting with at least one light chain constant domain of a mouse ora human.

The phrase “immunoglobulin molecule” includes two immunoglobulin heavychains and two immunoglobulin light chains. The heavy chains may beidentical or different, and the light chains may be identical ordifferent.

The phrase “light chain” includes an immunoglobulin light chain sequencefrom any organism, and unless otherwise specified includes human κ and λlight chains and a VpreB, as well as surrogate light chains. Light chainvariable (VL) domains typically include three light chain CDRs and fourframework (FR) regions, unless otherwise specified. Generally, afull-length light chain includes, from amino terminus to carboxylterminus, a VL domain that includes FR1-CDR1-FR2-CDR2-FR3-CDR3-FR4, anda light chain constant domain. Light chains include those, e.g., that donot selectively bind either a first or a second epitope selectivelybound by the epitope-binding protein in which they appear. Light chainsalso include those that bind and recognize, or assist the heavy chainwith binding and recognizing, one or more epitopes selectively bound bythe epitope-binding protein in which they appear. Common light chainsare those derived from a human Vκ1-39Jκ5 gene segment or a humanVκ3-20Jκ1 gene segment, and include somatically mutated (e.g., affinitymatured) versions of the same.

The phrase “micromolar range” is intended to mean 1-999 micromolar; thephrase “nanomolar range” is intended to mean 1-999 nanomolar; the phrase“picomolar range” is intended to mean 1-999 picomolar.

The phrase “somatically mutated” includes reference to a nucleic acidsequence from a B cell that has undergone class-switching, wherein thenucleic acid sequence of an immunoglobulin variable region (e.g., aheavy chain variable domain or including a heavy chain CDR or FRsequence) in the class-switched B cell is not identical to the nucleicacid sequence in the B cell prior to class-switching, such as, forexample, a difference in a CDR or framework nucleic acid sequencebetween a B cell that has not undergone class-switching and a B cellthat has undergone class-switching. “Somatically mutated” includesreference to nucleic acid sequences from affinity-matured B cells thatare not identical to corresponding immunoglobulin variable regionsequences in B cells that are not affinity-matured (i.e., sequences inthe genome of germline cells). The phrase “somatically mutated” alsoincludes reference to an immunoglobulin variable region nucleic acidsequence from a B cell after exposure of the B cell to an epitope ofinterest, wherein the nucleic acid sequence differs from thecorresponding nucleic acid sequence prior to exposure of the B cell tothe epitope of interest. The phrase “somatically mutated” refers tosequences from antibodies that have been generated in an animal, e.g., amouse having human immunoglobulin variable region nucleic acidsequences, in response to an immunogen challenge, and that result fromthe selection processes inherently operative in such an animal.

The term “unrearranged,” with reference to a nucleic acid sequence,includes nucleic acid sequences that exist in the germline of an animalcell.

The phrase “variable domain” includes an amino acid sequence of animmunoglobulin light or heavy chain (modified as desired) that comprisesthe following amino acid regions, in sequence from N-terminal toC-terminal (unless otherwise indicated): FR1, CDR1, FR2, CDR2, FR3,CDR3, FR4.

Common Light Chain

Prior efforts to make useful multispecific epitope-binding proteins,e.g., bispecific antibodies, have been hindered by variety of problemsthat frequently share a common paradigm: in vitro selection ormanipulation of sequences to rationally engineer, or to engineer throughtrial-and-error, a suitable format for pairing a heterodimericbispecific human immunoglobulin. Unfortunately, most if not all of thein vitro engineering approaches provide largely ad hoc fixes that aresuitable, if at all, for individual molecules. On the other hand, invivo methods for employing complex organisms to select appropriatepairings that are capable of leading to human therapeutics have not beenrealized.

Generally, native mouse sequences are frequently not a good source forhuman therapeutic sequences. For at least that reason, generating mouseheavy chain immunoglobulin variable regions that pair with a commonhuman light chain is of limited practical utility. More in vitroengineering efforts would be expended in a trial-and-error process totry to humanize the mouse heavy chain variable sequences while hoping toretain epitope specificity and affinity while maintaining the ability tocouple with the common human light chain, with uncertain outcome. At theend of such a process, the final product may maintain some of thespecificity and affinity, and associate with the common light chain, butultimately immunogenicity in a human would likely remain a profoundrisk.

Therefore, a suitable mouse for making human therapeutics would includea suitably large repertoire of human heavy chain variable region genesegments in place of endogenous mouse heavy chain variable region genesegments. The human heavy chain variable region gene segments should beable to rearrange and recombine with an endogenous mouse heavy chainconstant domain to form a reverse chimeric heavy chain (i.e., a heavychain comprising a human variable domain and a mouse constant region).The heavy chain should be capable of class switching and somatichypermutation so that a suitably large repertoire of heavy chainvariable domains are available for the mouse to select one that canassociate with the limited repertoire of human light chain variableregions.

A mouse that selects a common light chain for a plurality of heavychains has a practical utility. In various embodiments, antibodies thatexpress in a mouse that can only express a common light chain will haveheavy chains that can associate and express with an identical orsubstantially identical light chain. This is particularly useful inmaking bispecific antibodies. For example, such a mouse can be immunizedwith a first immunogen to generate a B cell that expresses an antibodythat specifically binds a first epitope. The mouse (or a mousegenetically the same) can be immunized with a second immunogen togenerate a B cell that expresses an antibody that specifically binds thesecond epitope. Variable heavy regions can be cloned from the B cellsand expresses with the same heavy chain constant region, and the samelight chain, and expressed in a cell to make a bispecific antibody,wherein the light chain component of the bispecific antibody has beenselected by a mouse to associate and express with the light chaincomponent.

The inventors have engineered a mouse for generating immunoglobulinlight chains that will suitably pair with a rather diverse family ofheavy chains, including heavy chains whose variable regions depart fromgermline sequences, e.g., affinity matured or somatically mutatedvariable regions. In various embodiments, the mouse is devised to pairhuman light chain variable domains with human heavy chain variabledomains that comprise somatic mutations, thus enabling a route to highaffinity binding proteins suitable for use as human therapeutics.

The genetically engineered mouse, through the long and complex processof antibody selection within an organism, makes biologically appropriatechoices in pairing a diverse collection of human heavy chain variabledomains with a limited number of human light chain options. In order toachieve this, the mouse is engineered to present a limited number ofhuman light chain variable domain options in conjunction with a widediversity of human heavy chain variable domain options. Upon challengewith an immunogen, the mouse maximizes the number of solutions in itsrepertoire to develop an antibody to the immunogen, limited largely orsolely by the number or light chain options in its repertoire. Invarious embodiments, this includes allowing the mouse to achievesuitable and compatible somatic mutations of the light chain variabledomain that will nonetheless be compatible with a relatively largevariety of human heavy chain variable domains, including in particularsomatically mutated human heavy chain variable domains.

To achieve a limited repertoire of light chain options, the mouse isengineered to render nonfunctional or substantially nonfunctional itsability to make, or rearrange, a native mouse light chain variabledomain. This can be achieved, e.g., by deleting the mouse's light chainvariable region gene segments. The endogenous mouse locus can then bemodified by an exogenous suitable human light chain variable region genesegment of choice, operably linked to the endogenous mouse light chainconstant domain, in a manner such that the exogenous human variableregion gene segments can rearrange and recombine with the endogenousmouse light chain constant region gene and form a rearranged reversechimeric light chain gene (human variable, mouse constant). In variousembodiments, the light chain variable region is capable of beingsomatically mutated. In various embodiments, to maximize ability of thelight chain variable region to acquire somatic mutations, theappropriate enhancer(s) is retained in the mouse. For example, inmodifying a mouse κ locus to replace endogenous mouse κ variable regiongene segments with human κ variable region gene segments, the mouse κintronic enhancer and mouse κ 3′ enhancer are functionally maintained,or undisrupted.

A genetically engineered mouse is provided that expresses a limitedrepertoire of reverse chimeric (human variable, mouse constant) lightchains associated with a diversity of reverse chimeric (human variable,mouse constant) heavy chains. In various embodiments, the endogenousmouse κ light chain variable region gene segments are deleted andreplaced with a single (or two) human light chain variable region genesegments, operably linked to the endogenous mouse κ constant regiongene. In embodiments for maximizing somatic hypermutation of the humanlight chain variable region gene segments, the mouse κ intronic enhancerand the mouse κ 3′ enhancer are maintained. In various embodiments, themouse also comprises a nonfunctional λ light chain locus, or a deletionthereof or a deletion that renders the locus unable to make a λ lightchain.

A genetically engineered mouse is provided that, in various embodiments,comprises a light chain variable region locus lacking an endogenousmouse light chain variable gene segment and comprising a human variablegene segment, in one embodiment a rearranged human V/J sequence,operably linked to a mouse constant region, wherein the locus is capableof undergoing somatic hypermutation, and wherein the locus expresses alight chain comprising the human V/J sequence linked to a mouse constantregion. Thus, in various embodiments, the locus comprises a mouse κ 3′enhancer, which is correlated with a normal, or wild-type, level ofsomatic hypermutation.

The genetically engineered mouse in various embodiments when immunizedwith an antigen of interest generates B cells that exhibit a diversityof rearrangements of human immunoglobulin heavy chain variable regionsthat express and function with one or with two rearranged light chains,including embodiments where the one or two light chains comprise humanlight chain variable regions that comprise, e.g., 1 to 5 somaticmutations. In various embodiments, the human light chains so expressedare capable of associating and expressing with any human immunoglobulinheavy chain variable region expressed in the mouse.

Epitope-Binding Proteins Binding More than One Epitope

The compositions and methods of described herein can be used to makebinding proteins that bind more than one epitope with high affinity,e.g., bispecific antibodies. Advantages of the invention include theability to select suitably high binding (e.g., affinity matured) heavychain immunoglobulin chains each of which will associate with a singlelight chain.

Synthesis and expression of bispecific binding proteins has beenproblematic, in part due to issues associated with identifying asuitable light chain that can associate and express with two differentheavy chains, and in part due to isolation issues. The methods andcompositions described herein allow for a genetically modified mouse toselect, through otherwise natural processes, a suitable light chain thatcan associate and express with more than one heavy chain, includingheavy chains that are somatically mutated (e.g., affinity matured).Human VL and VH sequences from suitable B cells of immunized mice asdescribed herein that express affinity matured antibodies having reversechimeric heavy chains (i.e., human variable and mouse constant) can beidentified and cloned in frame in an expression vector with a suitablehuman constant region gene sequence (e.g., a human IgG1). Two suchconstructs can be prepared, wherein each construct encodes a human heavychain variable domain that binds a different epitope. One of the humanVLs (e.g., human Vκ1-39Jκ5 or human Vκ3-20Jκ1), in germline sequence orfrom a B cell wherein the sequence has been somatically mutated, can befused in frame to a suitable human constant region gene (e.g., a human κconstant gene). These three fully-human heavy and light constructs canbe placed in a suitable cell for expression. The cell will express twomajor species: a homodimeric heavy chain with the identical light chain,and a heterodimeric heavy chain with the identical light chain. To allowfor a facile separation of these major species, one of the heavy chainsis modified to omit a Protein A-binding determinant, resulting in adifferential affinity of a homodimeric binding protein from aheterodimeric binding protein. Compositions and methods that addressthis issue are described in U.S. Ser. No. 12/832,838, filed 25 Jun.2010, entitled “Readily Isolated Bispecific Antibodies with NativeImmunoglobulin Format,” published as US 2010/0331527A1, herebyincorporated by reference.

In one aspect, an epitope-binding protein as described herein isprovided, wherein human VL and VH sequences are derived from micedescribed herein that have been immunized with an antigen comprising anepitope of interest.

In one embodiment, an epitope-binding protein is provided that comprisesa first and a second polypeptide, the first polypeptide comprising, fromN-terminal to C-terminal, a first epitope-binding region thatselectively binds a first epitope, followed by a constant region thatcomprises a first CH3 region of a human IgG selected from IgG1, IgG2,IgG4, and a combination thereof; and, a second polypeptide comprising,from N-terminal to C-terminal, a second epitope-binding region thatselectively binds a second epitope, followed by a constant region thatcomprises a second CH3 region of a human IgG selected from IgG1, IgG2,IgG4, and a combination thereof, wherein the second CH3 region comprisesa modification that reduces or eliminates binding of the second CH3domain to protein A.

In one embodiment, the second CH3 region comprises an H95R modification(by IMGT exon numbering; H435R by EU numbering). In another embodiment,the second CH3 region further comprises a Y96F modification (IMGT; Y436Fby EU).

In one embodiment, the second CH3 region is from a modified human IgG1,and further comprises a modification selected from the group consistingof D16E, L18M, N44S, K52N, V57M, and V82I (IMGT; D356E, L358M, N384S,K392N, V397M, and V422I by EU).

In one embodiment, the second CH3 region is from a modified human IgG2,and further comprises a modification selected from the group consistingof N44S, K52N, and V82I (IMGT; N384S, K392N, and V422I by EU).

In one embodiment, the second CH3 region is from a modified human IgG4,and further comprises a modification selected from the group consistingof Q15R, N44S, K52N, V57M, R69K, E79Q, and V82I (IMGT; Q355R, N384S,K392N, V397M, R409K, E419Q, and V422I by EU).

One method for making an epitope-binding protein that binds more thanone epitope is to immunize a first mouse in accordance with theinvention with an antigen that comprises a first epitope of interest,wherein the mouse comprises an endogenous immunoglobulin light chainvariable region locus that does not contain an endogenous mouse VL thatis capable of rearranging and forming a light chain, wherein at theendogenous mouse immunoglobulin light chain variable region locus is asingle human VL gene segment operably linked to the mouse endogenouslight chain constant region gene, and the human VL gene segment isselected from a human Vκ1-39Jκ5 and a human Vκ3-20Jκ1, and theendogenous mouse VH gene segments have been replaced in whole or in partwith human VH gene segments, such that immunoglobulin heavy chains madeby the mouse are solely or substantially heavy chains that comprisehuman variable domains and mouse constant domains. When immunized, sucha mouse will make a reverse chimeric antibody, comprising only one oftwo human light chain variable domains (e.g., one of human Vκ1-39Jκ5 orhuman Vκ3-20Jκ1). Once a B cell is identified that encodes a VH thatbinds the epitope of interest, the nucleotide sequence of the VH (and,optionally, the VL) can be retrieved (e.g., by PCR) and cloned into anexpression construct in frame with a suitable human immunoglobulinconstant domain. This process can be repeated to identify a second VHdomain that binds a second epitope, and a second VH gene sequence can beretrieved and cloned into an expression vector in frame to a secondsuitable immunoglobulin constant domain. The first and the secondimmunoglobulin constant domains can the same or different isotype, andone of the immunoglobulin constant domains (but not the other) can bemodified as described herein or in US 2010/0331527A1, andepitope-binding protein can be expressed in a suitable cell and isolatedbased on its differential affinity for Protein A as compared to ahomodimeric epitope-binding protein, e.g., as described in US2010/0331527A1.

In one embodiment, a method for making a bispecific epitope-bindingprotein is provided, comprising identifying a first affinity-matured(e.g., comprising one or more somatic hypermutations) human VHnucleotide sequence (VH1) from a mouse as described herein, identifyinga second affinity-matured (e.g., comprising one or more somatichypermutations) human VH nucleotide sequence (VH2) from a mouse asdescribed herein, cloning VH1 in frame with a human heavy chain lackinga Protein A-determinant modification as described in US 2010/0331527A1for form heavy chain 1 (HC1), cloning VH2 in frame with a human heavychain comprising a Protein A-determinant as described in US2010/0331527A1 to form heavy chain 2 (HC2), introducing an expressionvector comprising HC1 and the same or a different expression vectorcomprising HC2 into a cell, wherein the cell also expresses a humanimmunoglobulin light chain that comprises a human Vκ1-39/human Jκ5 or ahuman Vκ3-20/human Jκ1 fused to a human light chain constant domain,allowing the cell to express a bispecific epitope-binding proteincomprising a VH domain encoded by VH1 and a VH domain encoded by VH2,and isolating the bispecific epitope-binding protein based on itsdifferential ability to bind Protein A as compared with a monospecifichomodimeric epitope-binding protein. In a specific embodiment, HC1 is anIgG1, and HC2 is an IgG1 that comprises the modification H95R (IMGT;H435R by EU) and further comprises the modification Y96F (IMGT; Y436F byEU). In one embodiment, the VH domain encoded by VH1, the VH domainencoded by VH2, or both, are somatically mutated.

Human VH Genes that Express with a Common Human VL

A variety of human variable regions from affinity-matured antibodiesraised against four different antigens were expressed with either theircognate light chain, or at least one of a human light chain selectedfrom human Vκ1-39Jκ5, human Vκ3-20Jκ1, or human VpreBJλ5 (see Example1). For antibodies to each of the antigens, somatically mutated highaffinity heavy chains from different gene families paired successfullywith rearranged human germline Vκ1-39Jκ5 and Vκ3-20Jκ1 regions and weresecreted from cells expressing the heavy and light chains. For Vκ1-39Jκ5and Vκ3-20Jκ1, VH domains derived from the following human VH familiesexpressed favorably: 1-2, 1-8, 1-24, 2-5, 3-7, 3-9, 3-11, 3-13, 3-15,3-20, 3-23, 3-30, 3-33, 3-48, 4-31, 4-39, 4-59, 5-51, and 6-1. Thus, amouse that is engineered to express a limited repertoire of human VLdomains from one or both of Vκ1-39Jκ5 and Vκ3-20Jκ1 will generate adiverse population of somatically mutated human VH domains from a VHlocus modified to replace mouse VH gene segments with human VH genesegments.

Mice genetically engineered to express reverse chimeric (human variable,mouse constant) immunoglobulin heavy chains associated with a singlerearranged light chain (e.g., a Vκ1-39/J or a Vκ3-20/J), when immunizedwith an antigen of interest, generated B cells that comprised adiversity of human V segment rearrangements and expressed a diversity ofhigh-affinity antigen-specific antibodies with diverse properties withrespect to their ability to block binding of the antigen to its ligand,and with respect to their ability to bind variants of the antigen (seeExamples 5 through 10).

Thus, the mice and methods described herein are useful in making andselecting human immunoglobulin heavy chain variable domains, includingsomatically mutated human heavy chain variable domains, that result froma diversity of rearrangements, that exhibit a wide variety of affinities(including exhibiting a K_(D) of about a nanomolar or less), a widevariety of specificities (including binding to different epitopes of thesame antigen), and that associate and express with the same orsubstantially the same human immunoglobulin light chain variable region.

The following examples are provided so as to describe to those ofordinary skill in the art how to make and use methods and compositionsof the invention, and are not intended to limit the scope of what theinventors regard as their invention. Efforts have been made to ensureaccuracy with respect to numbers used (e.g., amounts, temperature, etc.)but some experimental errors and deviations should be accounted for.Unless indicated otherwise, parts are parts by weight, molecular weightis average molecular weight, temperature is indicated in Celsius, andpressure is at or near atmospheric.

EXAMPLES Example 1 Identification of Human Heavy Chain Variable Regionsthat Associate with Selected Human Light Chain Variable Regions

An in vitro expression system was constructed to determine if a singlerearranged human germline light chain could be co-expressed with humanheavy chains from antigen specific human antibodies.

Methods for generating human antibodies in genetically modified mice areknown (see e.g., U.S. Pat. No. 6,596,541, Regeneron Pharmaceuticals,VELOCIMMUNE®). The VELOCIMMUNE® technology involves generation of agenetically modified mouse having a genome comprising human heavy andlight chain variable regions operably linked to endogenous mouseconstant region loci such that the mouse produces an antibody comprisinga human variable region and a mouse constant region in response toantigenic stimulation. The DNA encoding the variable regions of theheavy and light chains of the antibodies produced from a VELOCIMMUNE®mouse are fully human. Initially, high affinity chimeric antibodies areisolated having a human variable region and a mouse constant region. Asdescribed below, the antibodies are characterized and selected fordesirable characteristics, including affinity, selectivity, epitope,etc. The mouse constant regions are replaced with a desired humanconstant region to generate a fully human antibody containing a non-IgMisotype, for example, wild-type or modified IgG1, IgG2, IgG3 or IgG4.While the constant region selected may vary according to specific use,high affinity antigen-binding and target specificity characteristicsreside in the variable region.

A VELOCIMMUNE® mouse was immunized with a growth factor that promotesangiogenesis (Antigen C) and antigen-specific human antibodies wereisolated and sequenced for V gene usage using standard techniquesrecognized in the art. Selected antibodies were cloned onto human heavyand light chain constant regions and 69 heavy chains were selected forpairing with one of three human light chains: (1) the cognate κ lightchain linked to a human κ constant region, (2) a rearranged humangermline Vκ1-39Jκ5 linked to a human κ constant region, or (3) arearranged human germline Vκ3-20Jκ1 linked to a human κ constant region.Each heavy chain and light chain pair were co-transfected in CHO-K1cells using standard techniques. Presence of antibody in the supernatantwas detected by anti-human IgG in an ELISA assay. Antibody titer (ng/ml)was determined for each heavy chain/light chain pair and titers with thedifferent rearranged germline light chains were compared to the titersobtained with the parental antibody molecule (i.e., heavy chain pairedwith cognate light chain) and percent of native titer was calculated(Table 1). V_(H): Heavy chain variable gene. ND: no expression detectedunder current experimental conditions.

TABLE 1 Antibody Titer (ng/ml) Percent of Native Titer Cognate Vκ1-V_(H) LC Vκ1-39Jκ5 Vκ3-20Jκ1 39Jκ5 Vκ3-20Jκ1 3-15 63 23 11 36.2 17.5 1-2103 53 ND 51.1 — 3-23 83 60 23 72.0 27.5 3-33 15 77 ND 499.4 — 4-31 2269 17 309.4 76.7 3-7 53 35 28 65.2 53.1 — 22 32 19 148.8 89.3 1-24 3 13ND 455.2 — 3-33 1 47 ND 5266.7 — 3-33 58 37 ND 63.1 — — 110 67 18 60.616.5 3-23 127 123 21 96.5 16.3 3-33 28 16 2 57.7 7.1 3-23 32 50 38 157.1119.4 — 18 45 18 254.3 101.7 3-9 1 30 23 2508.3 1900.0 3-11 12 26 6225.9 48.3 1-8 16 ND 13 — 81.8 3-33 54 81 10 150.7 19.1 — 34 9 ND 25.9 —3-20 7 14 54 203.0 809.0 3-33 19 38 ND 200.5 — 3-11 48 ND 203 — 423.6 —11 23 8 212.7 74.5 3-33 168 138 182 82.0 108.2 3-20 117 67 100 57.5 86.13-23 86 61 132 70.7 154.1 3-33 20 12 33 60.9 165.3 4-31 69 92 52 133.875.0 3-23 87 78 62 89.5 71.2 1-2 31 82 51 263.0 164.6 3-23 53 93 151175.4 285.4 — 11 8 17 75.7 151.4 3-33 114 36 27 31.6 23.4 3-15 73 39 4453.7 59.6 3-33 1 34 16 5600.0 2683.3 3-9 58 112 57 192.9 97.6 3-33 67 20105 30.1 157.0 3-33 34 21 24 62.7 70.4 3-20 10 49 91 478.4 888.2 3-33 6632 25 48.6 38.2 3-23 17 59 56 342.7 329.8 — 58 108 19 184.4 32.9 — 68 5420 79.4 29.9 3-33 42 35 32 83.3 75.4 — 29 19 13 67.1 43.9 3-9 24 34 29137.3 118.4 3-30/33 17 33 7 195.2 43.1 3-7 25 70 74 284.6 301.6 3-33 87127 ND 145.1 — 6-1 28 56 ND 201.8 — 3-33 56 39 20 69.9 36.1 3-33 10 53 1520.6 6.9 3-33 20 67 10 337.2 52.3 3-33 11 36 18 316.8 158.4 3-23 12 4232 356.8 272.9 3-33 66 95 15 143.6 22.5 3-15 55 68 ND 123.1 — — 32 68 3210.9 10.6 1-8 28 48 ND 170.9 — 3-33 124 192 21 154.3 17.0 3-33 0 113 ND56550.0 — 3-33 10 157 1 1505.8 12.5 3-33 6 86 15 1385.5 243.5 3-23 70115 22 163.5 31.0 3-7 71 117 21 164.6 29.6 3-33 82 100 47 122.7 57.1 3-7124 161 41 130.0 33.5

In a similar experiment, VELOCIMMUNE® mice were immunized with severaldifferent antigens and selected heavy chains of antigen specific humanantibodies were tested for their ability to pair with differentrearranged human germline light chains (as described above). Theantigens used in this experiment included an enzyme involved incholesterol homeostasis (Antigen A), a serum hormone involved inregulating glucose homeostasis (Antigen B), a growth factor thatpromotes angiogenesis (Antigen C) and a cell-surface receptor (AntigenD). Antigen specific antibodies were isolated from mice of eachimmunization group and the heavy chain and light chain variable regionswere cloned and sequenced. From the sequence of the heavy and lightchains, V gene usage was determined and selected heavy chains werepaired with either their cognate light chain or a rearranged humangermline Vκ1-39Jκ5 region. Each heavy/light chain pair wasco-transfected in CHO-K1 cells and the presence of antibody in thesupernatant was detected by anti-human IgG in an ELISA assay. Antibodytiter (μg/ml) was determined for each heavy chain/light chain pairingand titers with the different rearranged human germline light chainswere compared to the titers obtained with the parental antibody molecule(i.e., heavy chain paired with cognate light chain) and percent ofnative titer was calculated (Table 2). V_(H): Heavy chain variable gene.Vκ: κ light chain variable gene. ND: no expression detected undercurrent experimental conditions.

TABLE 2 Titer (μg/ml) V_(H) + Percent of Antigen Antibody V_(H) Vκ V_(H)Alone V_(H) + Vκ Vκ1-39Jκ5 Native Titer A 320 1-18 2-30 0.3 3.1 2.0 66321 2-5 2-28 0.4 0.4 1.9 448 334 2-5 2-28 0.4 2.7 2.0 73 313 3-13 3-150.5 0.7 4.5 670 316 3-23 4-1 0.3 0.2 4.1 2174 315 3-30 4-1 0.3 0.2 3.21327 318 4-59 1-17 0.3 4.6 4.0 86 B 257 3-13 1-5 0.4 3.1 3.2 104 2833-13 1-5 0.4 5.4 3.7 69 637 3-13 1-5 0.4 4.3 3.0 70 638 3-13 1-5 0.4 4.13.3 82 624 3-23 1-17 0.3 5.0 3.9 79 284 3-30 1-17 0.3 4.6 3.4 75 6533-33 1-17 0.3 4.3 0.3 7 268 4-34 1-27 0.3 5.5 3.8 69 633 4-34 1-27 0.66.9 3.0 44 C 730 3-7 1-5 0.3 1.1 2.8 249 728 3-7 1-5 0.3 2.0 3.2 157 6913-9 3-20 0.3 2.8 3.1 109 749 3-33 3-15 0.3 3.8 2.3 62 750 3-33 1-16 0.33.0 2.8 92 724 3-33 1-17 0.3 2.3 3.4 151 706 3-33 1-16 0.3 3.6 3.0 84744 1-18 1-12 0.4 5.1 3.0 59 696 3-11 1-16 0.4 3.0 2.9 97 685 3-13 3-200.3 0.5 3.4 734 732 3-15 1-17 0.3 4.5 3.2 72 694 3-15 1-5 0.4 5.2 2.9 55743 3-23 1-12 0.3 3.2 0.3 10 742 3-23 2-28 0.4 4.2 3.1 74 693 3-23 1-120.5 4.2 4.0 94 D 136 3-23 2-28 0.4 5.0 2.7 55 155 3-30 1-16 0.4 1.0 2.2221 163 3-30 1-16 0.3 0.6 3.0 506 171 3-30 1-16 0.3 1.0 2.8 295 145 3-431-5 0.4 4.4 2.9 65 49 3-48 3-11 0.3 1.7 2.6 155 51 3-48 1-39 0.1 1.9 0.14 159 3-7 6-21 0.4 3.9 3.6 92 169 3-7 6-21 0.3 1.3 3.1 235 134 3-9 1-50.4 5.0 2.9 58 141 4-31 1-33 2.4 4.2 2.6 63 142 4-31 1-33 0.4 4.2 2.8 67

The results obtained from these experiments demonstrate that somaticallymutated, high affinity heavy chains from different gene families areable to pair with rearranged human germline Vκ1-39Jκ5 and Vκ3-20Jκ1regions and be secreted from the cell as a normal antibody molecule. Asshown in Table 1, antibody titer was increased for about 61% (42 of 69)heavy chains when paired with the rearranged human Vκ1-39Jκ5 light chainand about 29% (20 of 69) heavy chains when paired with the rearrangedhuman Vκ3-20Jκ1 light chain as compared to the cognate light chain ofthe parental antibody. For about 20% (14 of 69) of the heavy chains,both rearranged human germline light chains conferred an increase inexpression as compared to the cognate light chain of the parentalantibody. As shown in Table 2, the rearranged human germline Vκ1-39Jκ5region conferred an increase in expression of several heavy chainsspecific for a range of different classes of antigens as compared to thecognate light chain for the parental antibodies. Antibody titer wasincreased by more than two-fold for about 35% (15/43) of the heavychains as compared to the cognate light chain of the parentalantibodies. For two heavy chains (315 and 316), the increase was greaterthan ten-fold as compared to the parental antibody. Within all the heavychains that showed increase expression relative to the cognate lightchain of the parental antibody, family three (V_(H)3) heavy chains areover represented in comparison to other heavy chain variable region genefamilies. This demonstrates a favorable relationship of human V_(H)3heavy chains to pair with rearranged human germline Vκ1-39Jκ5 andVκ3-20Jκ1 light chains.

Example 2 Generation of a Rearranged Human Germline Light Chain Locus

Various rearranged human germline light chain targeting vectors weremade using VELOCIGENE® technology (see, e.g., U.S. Pat. No. 6,586,251and Valenzuela et al. (2003) High-throughput engineering of the mousegenome coupled with high-resolution expression analysis, Nature Biotech.21(6):652-659) to modify mouse genomic Bacterial Artificial Chromosome(BAC) clones 302g12 and 254m04 (Invitrogen). Using these two BAC clones,genomic constructs were engineered to contain a single rearranged humangermline light chain region and inserted into an endogenous κ lightchain locus that was previously modified to delete the endogenous κvariable and joining gene segments.

A. Construction of Rearranged Human Germline Light Chain TargetingVectors

Three different rearranged human germline light chain regions were madeusing standard molecular biology techniques recognized in the art. Thehuman variable gene segments used for constructing these three regionsincluded rearranged human Vκ1-39Jκ5 sequence, a rearranged humanVκ3-20Jκ1 sequence and a rearranged human VpreBJλ5 sequence.

A DNA segment containing exon 1 (encoding the leader peptide) and intron1 of the mouse Vκ3-7 gene was made by de novo DNA synthesis (IntegratedDNA Technologies). Part of the 5′ untranslated region up to a naturallyoccurring BlpI restriction enzyme site was included. Exons of humanVκ1-39 and Vκ3-20 genes were PCR amplified from human genomic BAClibraries. The forward primers had a 5′ extension containing the spliceacceptor site of intron 1 of the mouse Vκ3-7 gene. The reverse primerused for PCR of the human Vκ1-39 sequence included an extension encodinghuman Jκ5, whereas the reverse primer used for PCR of the human Vκ3-20sequence included an extension encoding human Jκ1. The human VpreBJλ5sequence was made by de novo DNA synthesis (Integrated DNATechnologies). A portion of the human Jκ-Cκ intron including the splicedonor site was PCR amplified from plasmid pBS-296-HA18-PIScel. Theforward PCR primer included an extension encoding part of either a humanJκ5, Jκ1, or Jλ5 sequence. The reverse primer included a PI-Scel site,which was previously engineered into the intron.

The mouse Vκ3-7 exon1/intron 1, human variable light chain exons, andhuman Jκ-Cκ intron fragments were sewn together by overlap extensionPCR, digested with Blpl and PI-Scel, and ligated into plasmidpBS-296-HA18-PlScel, which contained the promoter from the human Vκ3-15variable gene segment. A loxed hygromycin cassette within plasmidpBS-296-HA18-PIScel was replaced with a FRTed hygromycin cassetteflanked by NotI and AscI sites. The NotI/PI-Scel fragment of thisplasmid was ligated into modified mouse BAC 254m04, which contained partof the mouse Jκ-Cκ intron, the mouse Cκ exon, and about 75 kb of genomicsequence downstream of the mouse κ locus which provided a 3′ homologyarm for homologous recombination in mouse ES cells. The NotI/AscIfragment of this BAC was then ligated into modified mouse BAC 302g12,which contained a FRTed neomycin cassette and about 23 kb of genomicsequence upstream of the endogenous κ locus for homologous recombinationin mouse ES cells.

B. Rearranged Human Germline Vκ1-39Jκ5 Targeting Vector (FIG. 1)

Restriction enzyme sites were introduced at the 5′ and 3′ ends of anengineered light chain insert for cloning into a targeting vector: anAscI site at the 5′ end and a PI-Scel site at the 3′ end. Within the 5′AscI site and the 3′ PI-Scel site the targeting construct from 5′ to 3′included a 5′ homology arm containing sequence 5′ to the endogenousmouse κ light chain locus obtained from mouse BAC clone 302g12, a FRTedneomycin resistance gene, an genomic sequence including the human Vκ3-15promoter, a leader sequence of the mouse Vκ3-7 variable gene segment, aintron sequence of the mouse Vκ3-7 variable gene segment, an openreading frame of a rearranged human germline Vκ1-39Jκ5 region, a genomicsequence containing a portion of the human Jκ-Cκ intron, and a 3′homology arm containing sequence 3′ of the endogenous mouse Jκ5 genesegment obtained from mouse BAC clone 254m04 (FIG. 1, middle). Genesand/or sequences upstream of the endogenous mouse K light chain locusand downstream of the most 3′ Jκ gene segment (e.g., the endogenous 3′enhancer) were unmodified by the targeting construct (see FIG. 1). Thesequence of the engineered human Vκ1-39Jκ5 locus is shown in SEQ IDNO:1.

Targeted insertion of the rearranged human germline Vκ1-39Jκ5 regioninto BAC DNA was confirmed by polymerase chain reaction (PCR) usingprimers located at sequences within the rearranged human germline lightchain region. Briefly, the intron sequence 3′ to the mouse Vκ3-7 leadersequence was confirmed with primers ULC-m1F (AGGTGAGGGT ACAGATAAGTGTTATGAG; SEQ ID NO:2) and ULC-m1R (TGACAAATGC CCTAATTATA GTGATCA; SEQID NO:3). The open reading frame of the rearranged human germlineVκ1-39Jκ5 region was confirmed with primers 1633-h2F (GGGCAAGTCAGAGCATTAGC A; SEQ ID NO:4) and 1633-h2R (TGCAAACTGG ATGCAGCATA G; SEQ IDNO:5). The neomycin cassette was confirmed with primers neoF (GGTGGAGAGGCTATTCGGC; SEQ ID NO:6) and neoR (GAACACGGCG GCATCAG; SEQ ID NO:7).Targeted BAC DNA was then used to electroporate mouse ES cells tocreated modified ES cells for generating chimeric mice that express arearranged human germline Vκ1-39Jκ5 region.

Positive ES cell clones were confirmed by TAQMAN™ screening andkaryotyping using probes specific for the engineered Vκ1-39Jκ5 lightchain region inserted into the endogenous locus. Briefly, probe neoP(TGGGCACAAC AGACAATCGG CTG; SEQ ID NO:8) which binds within the neomycinmarker gene, probe ULC-m1P (CCATTATGAT GCTCCATGCC TCTCTGTTC; SEQ IDNO:9) which binds within the intron sequence 3′ to the mouse Vκ3-7leader sequence, and probe 1633h2P (ATCAGCAGAA ACCAGGGAAA GCCCCT; SEQ IDNO:10) which binds within the rearranged human germline Vκ1-39Jκ5 openreading frame. Positive ES cell clones were then used to implant femalemice to give rise to a litter of pups expressing the germline Vκ1-39Jκ5light chain region.

Alternatively, ES cells bearing the rearranged human germline Vκ1-39Jκ5light chain region are transfected with a construct that expresses FLPin order to remove the FRTed neomycin cassette introduced by thetargeting construct. Optionally, the neomycin cassette is removed bybreeding to mice that express FLP recombinase (e.g., U.S. Pat. No.6,774,279). Optionally, the neomycin cassette is retained in the mice

C. Rearranged Human Germline Vκ3-20Jκ1 Targeting Vector (FIG. 2)

In a similar fashion, an engineered light chain locus expressing arearranged human germline Vκ3-20Jκ1 region was made using a targetingconstruct including, from 5′ to 3′, a 5′ homology arm containingsequence 5′ to the endogenous mouse κ light chain locus obtained frommouse BAC clone 302g12, a FRTed neomycin resistance gene, a genomicsequence including the human Vκ3-15 promoter, a leader sequence of themouse Vκ3-7 variable gene segment, an intron sequence of the mouse Vκ3-7variable gene segment, an open reading frame of a rearranged humangermline Vκ3-20Jκ1 region, a genomic sequence containing a portion ofthe human Jκ-Cκ intron, and a 3′ homology arm containing sequence 3′ ofthe endogenous mouse Jκ5 gene segment obtained from mouse BAC clone254m04 (FIG. 2, middle). The sequence of the engineered human Vκ3-20Jκ1locus is shown in SEQ ID NO:11.

Targeted insertion of the rearranged human germline Vκ3-20Jκ1 regioninto BAC DNA was confirmed by polymerase chain reaction (PCR) usingprimers located at sequences within the rearranged human germlineVκ3-20Jκ1 light chain region. Briefly, the intron sequence 3′ to themouse Vκ3-7 leader sequence was confirmed with primers ULC-m1F (SEQ IDNO:2) and ULC-m1R (SEQ ID NO:3). The open reading frame of therearranged human germline Vκ3-20Jκ1 region was confirmed with primers1635-h2F (TCCAGGCACC CTGTCTTTG; SEQ ID NO:12) and 1635-h2R (AAGTAGCTGCTGCTAACACT CTGACT; SEQ ID NO:13). The neomycin cassette was confirmedwith primers neoF (SEQ ID NO:6) and neoR (SEQ ID NO:7). Targeted BAC DNAwas then used to electroporate mouse ES cells to created modified EScells for generating chimeric mice that express the rearranged humangermline Vκ3-20J1 light chain.

Positive ES cell clones were confirmed by Taqman™ screening andkaryotyping using probes specific for the engineered Vκ3-20Jκ1 lightchain region inserted into the endogenous κ light chain locus. Briefly,probe neoP (SEQ ID NO:8) which binds within the neomycin marker gene,probe ULC-m1P (SEQ ID NO:9) which binds within the mouse Vκ3-7 leadersequence, and probe 1635h2P (AAAGAGCCAC CCTCTCCTGC AGGG; SEQ ID NO:14)which binds within the human Vκ3-20Jκ1 open reading frame. Positive EScell clones were then used to implant female mice. A litter of pupsexpressing the human germline Vκ3-20Jκ1 light chain region.

Alternatively, ES cells bearing human germline Vκ3-20Jκ1 light chainregion can be transfected with a construct that expresses FLP in oder toremove the FRTed neomycin cassette introduced by the targetingconstruct. Optionally, the neomycin cassette may be removed by breedingto mice that express FLP recombinase (e.g., U.S. Pat. No. 6,774,279).Optionally, the neomycin cassette is retained in the mice.

D. Rearranged Human Germline VpreBJλ5 Targeting Vector (FIG. 3)

In a similar fashion, an engineered light chain locus expressing arearranged human germline VpreBJλ5 region was made using a targetingconstruct including, from 5′ to 3′, a 5′ homology arm containingsequence 5′ to the endogenous mouse κ light chain locus obtained frommouse BAC clone 302g12, a FRTed neomycin resistance gene, an genomicsequence including the human Vκ3-15 promoter, a leader sequence of themouse Vκ3-7 variable gene segment, an intron sequence of the mouse Vκ3-7variable gene segment, an open reading frame of a rearranged humangermline VpreBJλ5 region, a genomic sequence containing a portion of thehuman Jκ-Cκ intron, and a 3′ homology arm containing sequence 3′ of theendogenous mouse Jκ5 gene segment obtained from mouse BAC clone 254m04(FIG. 3, middle). The sequence of the engineered human VpreBJλ5 locus isshown in SEQ ID NO:15.

Targeted insertion of the rearranged human germline VpreBJλ5 region intoBAC DNA was confirmed by polymerase chain reaction (PCR) using primerslocated at sequences within the rearranged human germline VpreBJλ5region light chain region. Briefly, the intron sequence 3′ to the mouseVκ3-7 leader sequence was confirmed with primers ULC-m1F (SEQ ID NO:2)and ULC-m1R (SEQ ID NO:3). The open reading frame of the rearrangedhuman germline VpreBJλ5 region was confirmed with primers 1616-h1F(TGTCCTCGGC CCTTGGA; SEQ ID NO:16) and 1616-h1R(CCGATGTCAT GGTCGTTCCT;SEQ ID NO:17). The neomycin cassette was confirmed with primers neoF(SEQ ID NO:6) and neoR (SEQ ID NO:7). Targeted BAC DNA was then used toelectroporate mouse ES cells to created modified ES cells for generatingchimeric mice that express the rearranged human germline VpreBJλ5 lightchain.

Positive ES cell clones are confirmed by TAQMAN™ screening andkaryotyping using probes specific for the engineered VpreBJλ5 lightchain region inserted into the endogenous κ light chain locus. Briefly,probe neoP (SEQ ID NO:8) which binds within the neomycin marker gene,probe ULC-m1P (SEQ ID NO:9) which binds within the mouse IgVκ3-7 leadersequence, and probe 1616h1P (ACAATCCGCC TCACCTGCAC CCT; SEQ ID NO:18)which binds within the human VpreBJλ5 open reading frame. Positive EScell clones are then used to implant female mice to give rise to alitter of pups expressing a germline light chain region.

Alternatively, ES cells bearing the rearranged human germline VpreBJλ5light chain region are transfected with a construct that expresses FLPin order to remove the FRTed neomycin cassette introduced by thetargeting construct. Optionally, the neomycin cassette is removed bybreeding to mice that express FLP recombinase (e.g., U.S. Pat. No.6,774,279). Optionally, the neomycin cassette is retained in the mice.

Example 3 Generation of Mice Expressing a Single Rearranged HumanGermline Light Chain

Targeted ES cells described above were used as donor ES cells andintroduced into an 8-cell stage mouse embryo by the VELOCIMOUSE® method(see, e.g., U.S. Pat. No. 7,294,754 and Poueymirou et al. (2007) F0generation mice that are essentially fully derived from the donorgene-targeted ES cells allowing immediate phenotypic analyses NatureBiotech. 25(1):91-99. VELOCIMICE® independently bearing an engineeredhuman germline Vκ1-39Jκ5 light chain region, a Vκ3-20Jκ1 light chainregion or a VpreBJλ5 light chain region are identified by genotypingusing a modification of allele assay (Valenzuela et al., supra) thatdetects the presence of the unique rearranged human germline light chainregion.

Pups are genotyped and a pup heterozygous for the unique rearrangedhuman germline light chain region are selected for characterizingexpression of the rearranged human germline light chain region.

Example 4 Breeding of Mice Expressing a Single Rearranged Human GermlineLight Chain A. Endogenous Igλ Knockout (KO).

To optimize the usage of the engineered light chain locus, mice bearingone of the rearranged human germline light chain regions are bred toanother mouse containing a deletion in the endogenous λ light chainlocus. In this manner, the progeny obtained will express, as their onlylight chain, the rearranged human germline light chain region asdescribed in Example 2. Breeding is performed by standard techniquesrecognized in the art and, alternatively, by a commercial breeder (e.g.,The Jackson Laboratory). Mouse strains bearing an engineered light chainlocus and a deletion of the endogenous λ light chain locus are screenedfor presence of the unique light chain region and absence of endogenousmouse λ light chains.

B. Humanized Endogenous Heavy Chain Locus.

Mice bearing an engineered human germline light chain locus are bredwith mice that contain a replacement of the endogenous mouse heavy chainvariable gene locus with the human heavy chain variable gene locus (seeU.S. Pat. No. 6,596,541; the VELOCIMMUNE® mouse, RegeneronPharmaceuticals, Inc.). The VELOCIMMUNE® mouse comprises a genomecomprising human heavy chain variable regions operably linked toendogenous mouse constant region loci such that the mouse producesantibodies comprising a human heavy chain variable region and a mouseheavy chain constant region in response to antigenic stimulation. TheDNA encoding the variable regions of the heavy chains of the antibodiesis isolated and operably linked to DNA encoding the human heavy chainconstant regions. The DNA is then expressed in a cell capable ofexpressing the fully human heavy chain of the antibody.

Mice bearing a replacement of the endogenous mouse VH locus with thehuman VH locus and a single rearranged human germline VL region at theendogenous κ light chain locus are obtained. Reverse chimeric antibodiescontaining somatically mutated heavy chains (human VH and mouse CH) witha single human light chain (human VL and mouse CL) are obtained uponimmunization with an antigen of interest. VH and VL nucleotide sequencesof B cells expressing the antibodies are identified and fully humanantibodies are made by fusion the VH and VL nucleotide sequences tohuman CH and CL nucleotide sequences in a suitable expression system.

Example 5 Generation of Antibodies from Mice Expressing Human HeavyChains and a Rearranged Human Germline Light Chain Region

After breeding mice that contain the engineered human light chain regionto various desired strains containing modifications and deletions ofother endogenous Ig loci (as described in Example 4), selected mice canbe immunized with an antigen of interest.

Generally, a VELOCIMMUNE® mouse containing one of the single rearrangedhuman germline light chain regions is challenged with an antigen, andlymphatic cells (such as B-cells) are recovered from serum of theanimals. The lymphatic cells are fused with a myeloma cell line toprepare immortal hybridoma cell lines, and such hybridoma cell lines arescreened and selected to identify hybridoma cell lines that produceantibodies containing human heavy chain variables and a rearranged humangermline light chains which are specific to the antigen used forimmunization. DNA encoding the variable regions of the heavy chains andthe light chain are isolated and linked to desirable isotypic constantregions of the heavy chain and light chain. Due to the presence of theendogenous mouse sequences and any additional cis-acting elementspresent in the endogenous locus, the single light chain of each antibodymay be somatically mutated. This adds additional diversity to theantigen-specific repertoire comprising a single light chain and diverseheavy chain sequences. The resulting cloned antibody sequences aresubsequently expressed in a cell, such as a CHO cell. Alternatively, DNAencoding the antigen-specific chimeric antibodies or the variabledomains of the light and heavy chains are identified directly fromantigen-specific lymphocytes.

Initially, high affinity chimeric antibodies are isolated having a humanvariable region and a mouse constant region. As described above, theantibodies are characterized and selected for desirable characteristics,including affinity, selectivity, epitope, etc. The mouse constantregions are replaced with a desired human constant region to generatethe fully human antibody containing a somatically mutated human heavychain and a single light chain derived from a rearranged human germlinelight chain region of the invention. Suitable human constant regionsinclude, for example wild-type or modified IgG1 or IgG4.

Separate cohorts of VELOCIMMUNE® mice containing a replacement of theendogenous mouse heavy chain locus with human V, D, and J gene segmentsand a replacement of the endogenous mouse κ light chain locus witheither the engineered germline Vκ1-39Jκ5 human light chain region or theengineered germline Vκ3-20Jκ1 human light chain region (described above)were immunized with a human cell-surface receptor protein (Antigen E).Antigen E is administered directly onto the hind footpad of mice withsix consecutive injections every 3-4 days. Two to three micrograms ofAntigen E are mixed with 10 μg of CpG oligonucleotide (Cat#tlrl-modn—ODN1826 oligonucleotide; InVivogen, San Diego, Calif.) and 25μg of Adju-Phos (Aluminum phosphate gel adjuvant, Cat#H-71639-250;Brenntag Biosector, Frederikssund, Denmark) prior to injection. A totalof six injections are given prior to the final antigen recall, which isgiven 3-5 days prior to sacrifice. Bleeds after the 4th and 6thinjection are collected and the antibody immune response is monitored bya standard antigen-specific immunoassay.

When a desired immune response is achieved splenocytes are harvested andfused with mouse myeloma cells to preserve their viability and formhybridoma cell lines. The hybridoma cell lines are screened and selectedto identify cell lines that produce Antigen E-specific common lightchain antibodies. Using this technique several anti-Antigen E-specificcommon light chain antibodies (i.e., antibodies possessing human heavychain variable domains, the same human light chain variable domain, andmouse constant domains) are obtained.

Alternatively, anti-Antigen E common light chain antibodies are isolateddirectly from antigen-positive B cells without fusion to myeloma cells,as described in U.S. 2007/0280945A1, herein specifically incorporated byreference in its entirety. Using this method, several fully humananti-Antigen E common light chain antibodies (i.e., antibodiespossessing human heavy chain variable domains, either an engineeredhuman Vκ1-39Jκ5 light chain or an engineered human Vκ3-20Jκ1 light chainregion, and human constant domains) were obtained.

The biological properties of the exemplary anti-Antigen E common lightchain antibodies generated in accordance with the methods of thisExample are described in detail in the sections set forth below.

Example 6 Heavy Chain Gene Segment Usage in Antigen-Specific CommonLight Chain Antibodies

To analyze the structure of the human anti-Antigen E common light chainantibodies produced, nucleic acids encoding heavy chain antibodyvariable regions were cloned and sequenced. From the nucleic acidsequences and predicted amino acid sequences of the antibodies, geneusage was identified for the heavy chain variable region (HCVR) ofselected common light chain antibodies obtained from immunizedVELOCIMMUNE® mice containing either the engineered human Vκ1-39Jκ5 lightchain or engineered human Vκ3-20Jκ1 light chain region. Results areshown in Tables 3 and 4, which demonstrate that mice according to theinvention generate antigen-specific common light chain antibodies from avariety of human heavy chain gene segments, due to a variety ofrearrangements, when employing either a mouse that expresses a lightchain from only a human Vκ1-39- or a human Vκ3-20-derived light chain.Human V_(H) gene segments of the 2, 3, 4, and 5 families rearranged witha variety of human D_(H) segments and human J_(H) segments to yieldantigen-specific antibodies.

TABLE 3 Vκ1-39Jκ5 Common Light Chain Antibodies HCVR Antibody V_(H)D_(H) J_(H) 2952 2-5  6-6 1 3022 3-23 3-10 4 3028 3-23 3-3 4 2955 3-306-6 1 3043 3-30 6-6 3 3014 3-30 1-7 4 3015 3-30 1-7 4 3023 3-30 1-7 43024 3-30 1-7 4 3032 3-30 1-7 4 3013 3-30 5-12 4 3042 3-30 5-12 4 29853-30 6-13 4 2997 3-30 6-13 4 3011 3-30 6-13 4 3047 3-30 6-13 4 3018 3-306-6 4 2948 3-30 7-27 4 2987 3-30 7-27 4 2996 3-30 7-27 4 3005 3-30 7-274 3012 3-30 7-27 4 3020 3-30 7-27 4 3021 3-30 7-27 4 3025 3-30 7-27 43030 3-30 7-27 4 3036 3-30 7-27 4 2982 3-30 3-22 5 2949 3-30 6-6 5 29503-30 6-6 5 2954 3-30 6-6 5 2978 3-30 6-6 5 3016 3-30 6-6 5 3017 3-30 6-65 3033 3-30 6-6 5 3041 3-30 6-6 5 3004 3-30 7-27 5 3010 4-59 3-16 3 30194-59 3-16 3 2964 4-59 3-22 3 3027 4-59 3-16 4 3046 5-51 5-5 3

TABLE 4 Vκ3-20Jκ1 Common Light Chain Antibodies HCVR Antibody V_(H)D_(H) J_(H) 2968 4-39 1-26 3 2975 5-51 6-13 5 2972 5-51 3-16 6

Example 7 Determination of Blocking Ability of Antigen-Specific CommonLight Chain Antibodies by Luminex™ Assay

Ninety-eight human common light chain antibodies raised against AntigenE were tested for their ability to block binding of Antigen E's naturalligand (Ligand Y) to Antigen E in a bead-based assay.

The extracellular domain (ECD) of Antigen E was conjugated to two mycepitope tags and a 6× histidine tag (Antigen E-mmH) and amine-coupled tocarboxylated microspheres at a concentration of 20 μg/mL in MES buffer.The mixture was incubated for two hours at room temperature followed bybead deactivation with 1M Tris pH 8.0 followed by washing in PBS with0.05% (v/v) Tween-20. The beads were then blocked with PBS (IrvineScientific, Santa Ana, Calif.) containing 2% (w/v) BSA (Sigma-AldrichCorp., St. Louis, Mo.). In a 96-well filter plate, supernatantscontaining Antigen E-specific common light chain antibodies, werediluted 1:15 in buffer. A negative control containing a mock supernatantwith the same media components as for the antibody supernatant wasprepared. Antigen E-labeled beads were added to the supernatants andincubated overnight at 4° C. Biotinylated-Ligand Y protein was added toa final concentration of 0.06 nM and incubated for two hours at roomtemperature. Detection of biotinylated-Ligand Y bound to AntigenE-myc-myc-6His labeled beads was determined with R-Phycoerythrinconjugated to Streptavidin (Moss Inc, Pasadena, Md.) followed bymeasurement in a Luminex™ flow cytometry-based analyzer. Background MeanFluorescence Intensity (MFI) of a sample without Ligand Y was subtractedfrom all samples. Percent blocking was calculated by division of thebackground-subtracted MFI of each sample by the adjusted negativecontrol value, multiplying by 100 and subtracting the resulting valuefrom 100.

In a similar experiment, the same 98 human common light chain antibodiesraised against Antigen E were tested for their ability to block bindingof Antigen E to Ligand Y-labeled beads.

Briefly, Ligand Y was amine-coupled to carboxylated microspheres at aconcentration of 20 μg/mL diluted in MES buffer. The mixture andincubated two hours at room temperature followed by deactivation ofbeads with 1M Tris pH 8 then washing in PBS with 0.05% (v/v) Tween-20.The beads were then blocked with PBS (Irvine Scientific, Santa Ana,Calif.) containing 2% (w/v) BSA (Sigma-Aldrich Corp., St. Louis, Mo.).In a 96-well filter plate, supernatants containing Antigen E-specificcommon light chain antibodies were diluted 1:15 in buffer. A negativecontrol containing a mock supernatant with the same media components asfor the antibody supernatant was prepared. A biotinylated-Antigen E-mmHwas added to a final concentration of 0.42 nM and incubated overnight at4° C. Ligand Y-labeled beads were then added to the antibody/Antigen Emixture and incubated for two hours at room temperature. Detection ofbiotinylated-Antigen E-mmH bound to Ligand Y-beads was determined withR-Phycoerythrin conjugated to Streptavidin (Moss Inc, Pasadena, Md.)followed by measurement in a Luminex™ flow cytometry-based analyzer.Background Mean Fluorescence Intensity (MFI) of a sample without AntigenE was subtracted from all samples. Percent blocking was calculated bydivision of the background-subtracted MFI of each sample by the adjustednegative control value, multiplying by 100 and subtracting the resultingvalue from 100.

Tables 5 and 6 show the percent blocking for all 98 anti-Antigen Ecommon light chain antibodies tested in both Luminex™ assays. ND: notdetermined under current experimental conditions.

In the first Luminex™ experiment described above, 80 common light chainantibodies containing the Vκ1-39Jκ5 engineered light chain were testedfor their ability to block Ligand Y binding to Antigen E-labeled beads.Of these 80 common light chain antibodies, 68 demonstrated >50%blocking, while 12 demonstrated <50% blocking (6 at 25-50% blocking and6 at <25% blocking). For the 18 common light chain antibodies containingthe Vκ3-20Jκ1 engineered light chain, 12 demonstrated >50% blocking,while 6 demonstrated <50% blocking (3 at 25-50% blocking and 3 at <25%blocking) of Ligand Y binding to Antigen E-labeled beads.

In the second Luminex™ experiment described above, the same 80 commonlight chain antibodies containing the Vκ1-39Jκ5 engineered light chainwere tested for their ability to block binding of Antigen E to LigandY-labeled beads. Of these 80 common light chain antibodies, 36demonstrated >50% blocking, while 44 demonstrated <50% blocking (27 at25-50% blocking and 17 at <25% blocking). For the 18 common light chainantibodies containing the Vκ3-20Jκ1 engineered light chain, 1demonstrated >50% blocking, while 17 demonstrated <50% blocking (5 at25-50% blocking and 12 at <25% blocking) of Antigen E binding to LigandY-labeled beads.

The data of Tables 5 and 6 establish that the rearrangements describedin Tables 3 and 4 generated anti-Antigen E-specific common light chainantibodies that blocked binding of Ligand Y to its cognate receptorAntigen E with varying degrees of efficacy, which is consistent with theanti-Antigen E common light chain antibodies of Tables 3 and 4comprising antibodies with overlapping and non-overlapping epitopespecificity with respect to Antigen E.

TABLE 5 Vκ1-39Jκ5 Common Light Chain Antibodies % Blocking of % Blockingof Antibody Antigen E-Labeled Beads Antigen E In Solution 2948 81.1 47.82948G 38.6 ND 2949 97.6 78.8 2949G 97.1 73.7 2950 96.2 81.9 2950G 89.831.4 2952 96.1 74.3 2952G 93.5 39.9 2954 93.7 70.1 2954G 91.7 30.1 295575.8 30.0 2955G 71.8 ND 2964 92.1 31.4 2964G 94.6 43.0 2978 98.0 95.12978G 13.9 94.1 2982 92.8 78.5 2982G 41.9 52.4 2985 39.5 31.2 2985G 2.05.0 2987 81.7 67.8 2987G 26.6 29.3 2996 87.3 55.3 2996G 95.9 38.4 299793.4 70.6 2997G 9.7 7.5 3004 79.0 48.4 3004G 60.3 40.7 3005 97.4 93.53005G 77.5 75.6 3010 98.0 82.6 3010G 97.9 81.0 3011 87.4 42.8 3011G 83.541.7 3012 91.0 60.8 3012G 52.4 16.8 3013 80.3 65.8 3013G 17.5 15.4 301463.4 20.7 3014G 74.4 28.5 3015 89.1 55.7 3015G 58.8 17.3 3016 97.1 81.63016G 93.1 66.4 3017 94.8 70.2 3017G 87.9 40.8 3018 85.4 54.0 3018G 26.112.7 3019 99.3 92.4 3019G 99.3 88.1 3020 96.7 90.3 3020G 85.2 41.5 302174.5 26.1 3021G 81.1 27.4 3022 65.2 17.6 3022G 67.2 9.1 3023 71.4 28.53023G 73.8 29.7 3024 73.9 32.6 3024G 89.0 10.0 3025 70.7 15.6 3025G 76.724.3 3027 96.2 61.6 3027G 98.6 75.3 3028 92.4 29.0 3028G 87.3 28.8 30306.0 10.6 3030G 41.3 14.2 3032 76.5 31.4 3032G 17.7 11.0 3033 98.2 86.13033G 93.6 64.0 3036 74.7 32.7 3036G 90.1 51.2 3041 95.3 75.9 3041G 92.451.6 3042 88.1 73.3 3042G 60.9 25.2 3043 90.8 65.8 3043G 92.8 60.3

TABLE 6 Vκ3-20Jκ1 Common Light Chain Antibodies % Blocking of % Blockingof Antibody Antigen E-Labeled Beads Antigen E In Solution 2968 97.1 73.32968G 67.1 14.6 2969 51.7 20.3 2969G 37.2 16.5 2970 92.2 34.2 2970G 92.727.2 2971 23.4 11.6 2971G 18.8 18.9 2972 67.1 38.8 2972G 64.5 39.2 297377.7 27.0 2973G 51.1 20.7 2974 57.8 12.4 2974G 69.9 17.6 2975 49.4 18.22975G 32.0 19.5 2976 1.0 1.0 2976G 50.4 20.4

Example 8 Determination of Blocking Ability of Antigen-Specific CommonLight Chain Antibodies by ELISA

Human common light chain antibodies raised against Antigen E were testedfor their ability to block Antigen E binding to a Ligand Y-coatedsurface in an ELISA assay.

Ligand Y was coated onto 96-well plates at a concentration of 2 μg/mLdiluted in PBS and incubated overnight followed by washing four times inPBS with 0.05% Tween-20. The plate was then blocked with PBS (IrvineScientific, Santa Ana, Calif.) containing 0.5% (w/v) BSA (Sigma-AldrichCorp., St. Louis, Mo.) for one hour at room temperature. In a separateplate, supernatants containing anti-Antigen E common light chainantibodies were diluted 1:10 in buffer. A mock supernatant with the samecomponents of the antibodies was used as a negative control. AntigenE-mmH (described above) was added to a final concentration of 0.150 nMand incubated for one hour at room temperature. The antibody/AntigenE-mmH mixture was then added to the plate containing Ligand Y andincubated for one hour at room temperature. Detection of Antigen E-mmHbound to Ligand Y was determined with Horse-Radish Peroxidase (HRP)conjugated to anti-Penta-His antibody (Qiagen, Valencia, Calif.) anddeveloped by standard colorimetric response using tetramethylbenzidine(TMB) substrate (BD Biosciences, San Jose, Calif.) neutralized bysulfuric acid. Absorbance was read at OD450 for 0.1 sec. Backgroundabsorbance of a sample without Antigen E was subtracted from allsamples. Percent blocking was calculated by division of thebackground-subtracted MFI of each sample by the adjusted negativecontrol value, multiplying by 100 and subtracting the resulting valuefrom 100.

Tables 7 and 8 show the percent blocking for all 98 anti-Antigen Ecommon light chain antibodies tested in the ELISA assay. ND: notdetermined under current experimental conditions.

As described in this Example, of the 80 common light chain antibodiescontaining the Vκ1-39Jκ5 engineered light chain tested for their abilityto block Antigen E binding to a Ligand Y-coated surface, 22demonstrated >50% blocking, while 58 demonstrated <50% blocking (20 at25-50% blocking and 38 at <25% blocking). For the 18 common light chainantibodies containing the Vκ3-20Jκ1 engineered light chain, 1demonstrated >50% blocking, while 17 demonstrated <50% blocking (5 at25-50% blocking and 12 at <25% blocking) of Antigen E binding to aLigand Y-coated surface.

These results are also consistent with the Antigen E-specific commonlight chain antibody pool comprising antibodies with overlapping andnon-overlapping epitope specificity with respect to Antigen E.

TABLE 7 Vκ1-39Jκ5 Common Light Chain Antibodies % Blocking of AntibodyAntigen E In Solution 2948 21.8 2948G 22.9 2949 79.5 2949G 71.5 295080.4 2950G 30.9 2952 66.9 2952G 47.3 2954 55.9 2954G 44.7 2955 12.12955G 25.6 2964 34.8 2964G 47.7 2978 90.0 2978G 90.2 2982 59.0 2982G20.4 2985 10.5 2985G ND 2987 31.4 2987G ND 2996 29.3 2996G ND 2997 48.72997G ND 3004 16.7 3004G 3.5 3005 87.2 3005G 54.3 3010 74.5 3010G 84.63011 19.4 3011G ND 3012 45.0 3012G 12.6 3013 39.0 3013G 9.6 3014 5.23014G 17.1 3015 23.7 3015G 10.2 3016 78.1 3016G 37.4 3017 61.6 3017G25.2 3018 40.6 3018G 14.5 3019 94.6 3019G 92.3 3020 80.8 3020G ND 30217.6 3021G 20.7 3022 2.4 3022G 15.0 3023 9.1 3023G 19.2 3024 7.5 3024G15.2 3025 ND 3025G 13.9 3027 61.4 3027G 82.7 3028 40.3 3028G 12.3 3030ND 3030G 9.5 3032 ND 3032G 13.1 3033 77.1 3033G 32.9 3036 17.6 3036G24.6 3041 59.3 3041G 30.7 3042 39.9 3042G 16.1 3043 57.4 3043G 46.1

TABLE 8 Vκ3-20Jκ1 Common Light Chain Antibodies % Blocking Antibody ofAntigen E In Solution 2968 68.9 2968G 15.2 2969 10.1 2969G 23.6 297034.3 2970G 41.3 2971 6.3 2971G 27.1 2972 9.6 2972G 35.7 2973 20.7 2973G23.1 2974 ND 2974G 22.0 2975 8.7 2975G 19.2 2976 4.6 2976G 26.7

Example 9 BIAcore™ Affinity Determination for Antigen-Specific CommonLight Chain Antibodies

Equilibrium dissociation constants (K_(D)) for selected antibodysupernatants were determined by SPR (Surface Plasmon Resonance) using aBIAcore™ T100 instrument (GE Healthcare). All data was obtained usingHBS-EP (10 mM Hepes, 150 mM NaCl, 0.3 mM EDTA, 0.05% Surfactant P20, pH7.4) as both the running and sample buffers, at 25° C. Antibodies werecaptured from crude supernatant samples on a CM5 sensor chip surfacepreviously derivatized with a high density of anti-human Fc antibodiesusing standard amine coupling chemistry. During the capture step,supernatants were injected across the anti-human Fc surface at a flowrate of 3 μL/min, for a total of 3 minutes. The capture step wasfollowed by an injection of either running buffer or analyte at aconcentration of 100 nM for 2 minutes at a flow rate of 35 μL/min.Dissociation of antigen from the captured antibody was monitored for 6minutes. The captured antibody was removed by a brief injection of 10 mMglycine, pH 1.5. All sensorgrams were double referenced by subtractingsensorgrams from buffer injections from the analyte sensorgrams, therebyremoving artifacts caused by dissociation of the antibody from thecapture surface. Binding data for each antibody was fit to a 1:1 bindingmodel with mass transport using BIAcore T100 Evaluation software v2.1.Results are shown in Tables 9 and 10.

The binding affinities of common light chain antibodies comprising therearrangements shown in Tables 3 and 4 vary, with nearly all exhibitinga K_(D) in the nanomolar range. The affinity data is consistent with thecommon light chain antibodies resulting from the combinatorialassociation of rearranged variable domains described in Tables 3 and 4being high-affinity, clonally selected, and somatically mutated. Coupledwith data previously shown, the common light chain antibodies describedin Tables 3 and 4 comprise a collection of diverse, high-affinityantibodies that exhibit specificity for one or more epitopes on AntigenE.

TABLE 9 Vκ1-39Jκ5 Common Light Chain Antibodies 100 nM Antigen EAntibody K_(D) (nM) T_(1/2) (min) 2948 8.83 28 2948G 95.0 1 2949 3.57 182949G 6.37 9 2950 4.91 17 2950G 13.6 5 2952 6.25 7 2952G 7.16 4 29542.37 24 2954G 5.30 9 2955 14.4 6 2955G 12.0 4 2964 14.8 6 2964G 13.0 92978 1.91 49 2978G 1.80 58 2982 6.41 19 2982G 16.3 9 2985 64.4 9 2985G2.44 8 2987 21.0 11 2987G 37.6 4 2996 10.8 9 2996G 24.0 2 2997 7.75 192997G 151 1 3004 46.5 14 3004G 1.93 91 3005 2.35 108 3005G 6.96 27 30104.13 26 3010G 2.10 49 3011 59.1 5 3011G 41.7 5 3012 9.71 20 3012G 89.9 23013 20.2 20 3013G 13.2 4 3014 213 4 3014G 36.8 3 3015 29.1 11 3015G65.9 0 3016 4.99 17 3016G 18.9 4 3017 9.83 8 3017G 55.4 2 3018 11.3 363018G 32.5 3 3019 1.54 59 3019G 2.29 42 3020 5.41 39 3020G 41.9 6 302150.1 6 3021G 26.8 4 3022 25.7 17 3022G 20.8 12 3023 263 9 3023G 103 53024 58.8 7 3024G 7.09 10 3025 35.2 6 3025G 42.5 8 3027 7.15 6 3027G4.24 18 3028 6.89 37 3028G 7.23 22 3030 46.2 7 3030G 128 3 3032 53.2 93032G 13.0 1 3033 4.61 17 3033G 12.0 5 3036 284 12 3036G 18.2 10 30416.90 12 3041G 22.9 2 3042 9.46 34 3042G 85.5 3 3043 9.26 29 3043G 13.122

TABLE 10 Vκ3-20Jκ1 Common Light Chain Antibodies 100 nM Antigen EAntibody K_(D) (nM) T_(1/2) (min) 2968 5.50 8 2968G 305 0 2969 34.9 22969G 181 1 2970G 12.3 3 2971G 32.8 22 2972 6.02 13 2972G 74.6 26 29735.35 39 2973G 11.0 44 2974 256 0 2974G 138 0 2975 38.0 2 2975G 134 12976 6.73 10 2976G 656 8

Example 10 Determination of Binding Specificities of Antigen-SpecificCommon Light Chain Antibodies by Luminex™ Assay

Selected anti-Antigen E common light chain antibodies were tested fortheir ability to bind to the ECD of Antigen E and Antigen E ECDvariants, including the cynomolgous monkey ortholog (Mf Antigen E),which differs from the human protein in approximately 10% of its aminoacid residues; a deletion mutant of Antigen E lacking the last 10 aminoacids from the C-terminal end of the ECD (Antigen E-ACT); and twomutants containing an alanine substitution at suspected locations ofinteraction with Ligand Y (Antigen E-Ala1 and AntigenE-Ala2). TheAntigen E proteins were produced in CHO cells and each contained amyc-myc-His C-terminal tag.

For the binding studies, Antigen E ECD protein or variant protein(described above) from 1 mL of culture medium was captured by incubationfor 2 hr at room temperature with 1×10⁶ microsphere (Luminex™) beadscovalently coated with an anti-myc monoclonal antibody (MAb 9E10,hybridoma cell line CRL-1729™; ATCC, Manassas, Va.). The beads were thenwashed with PBS before use. Supernatants containing anti-Antigen Ecommon light chain antibodies were diluted 1:4 in buffer and added to96-well filter plates. A mock supernatant with no antibody was used asnegative control. The beads containing the captured Antigen E proteinswere then added to the antibody samples (3000 beads per well) andincubated overnight at 4° C. The following day, the sample beads werewashed and the bound common light chain antibody was detected with aR-phycoerythrin-conjugated anti-human IgG antibody. The fluorescenceintensity of the beads (approximately 100 beads counted for eachantibody sample binding to each Antigen E protein) was measured with aLuminex™ flow cytometry-based analyzer, and the median fluorescenceintensity (MFI) for at least 100 counted beads per bead/antibodyinteraction was recorded. Results are shown in Tables 11 and 12.

TABLE 11 Vκ1-39Jκ5 Common Light Chain Antibodies Mean FluorescenceIntensity (MFI) Antigen E- Antigen Antigen Antigen Antibody ECD E-ΔCTE-Ala1 E-Ala2 Mf Antigen E 2948 1503 2746 4953 3579 1648 2948G 537 6622581 2150 863 2949 3706 4345 8169 5678 5142 2949G 3403 3318 7918 58265514 2950 3296 4292 7756 5171 4749 2950G 2521 2408 7532 5079 3455 29523384 1619 1269 168 911 2952G 3358 1001 108 55 244 2954 2808 3815 71145039 3396 2954G 2643 2711 7620 5406 3499 2955 1310 2472 4738 3765 16372955G 1324 1802 4910 3755 1623 2964 5108 1125 4185 346 44 2964G 4999 7294646 534 91 2978 6986 2800 14542 10674 8049 2978G 5464 3295 11652 80266452 2982 4955 2388 13200 9490 6772 2982G 3222 2013 8672 6509 4949 29851358 832 4986 3892 1669 2985G 43 43 128 244 116 2987 3117 1674 7646 59442546 2987G 3068 1537 9202 6004 4744 2996 4666 1917 12875 9046 6459 2996G2752 1736 8742 6150 4873 2997 5164 2159 12167 8361 5922 2997G 658 3563392 2325 1020 3004 2794 1397 8542 6268 3083 3004G 2753 1508 8267 58084345 3005 5683 2221 12900 9864 5868 3005G 4344 2732 10669 7125 5880 30104829 1617 2642 3887 44 3010G 3685 1097 2540 3022 51 3011 2859 2015 78555513 3863 3011G 2005 1072 6194 4041 3181 3012 3233 2221 8543 5637 33073012G 968 378 3115 2261 1198 3013 2343 1791 6715 4810 2528 3013G 327 1441333 1225 370 3014 1225 1089 5436 3621 1718 3014G 1585 851 5178 37052411 3015 3202 2068 8262 5554 3796 3015G 1243 531 4246 2643 1611 30164220 2543 8920 5999 5666 3016G 2519 1277 6344 4288 4091 3017 3545 25538700 5547 5098 3017G 1972 1081 5763 3825 3038 3018 2339 1971 6140 45152293 3018G 254 118 978 1020 345 3019 5235 1882 7108 4249 54 3019G 40901270 4769 3474 214 3020 3883 3107 8591 6602 4420 3020G 2165 1209 64894295 2912 3021 1961 1472 6872 4641 2742 3021G 2091 1005 6430 3988 29353022 2418 793 7523 2679 36 3022G 2189 831 6182 3051 132 3023 1692 14115788 3898 2054 3023G 1770 825 5702 3677 2648 3024 1819 1467 6179 45572450 3024G 100 87 268 433 131 3025 1853 1233 6413 4337 2581 3025G 1782791 5773 3871 2717 3027 4131 1018 582 2510 22 3027G 3492 814 1933 259642 3028 4361 2545 9884 5639 975 3028G 2835 1398 7124 3885 597 3030 463277 1266 1130 391 3030G 943 302 3420 2570 1186 3032 2083 1496 6594 44022405 3032G 295 106 814 902 292 3033 4409 2774 8971 6331 5825 3033G 24991234 6745 4174 4210 3036 1755 1362 6137 4041 1987 3036G 2313 1073 63874243 3173 3041 3674 2655 8629 5837 4082 3041G 2519 1265 6468 4274 33203042 2653 2137 7277 5124 3325 3042G 1117 463 4205 2762 1519 3043 30362128 7607 5532 3366 3043G 2293 1319 6573 4403 3228

TABLE 12 Vκ3-20Jκ1 Common Light Chain Antibodies Mean FluorescenceIntensity (MFI) Antigen E- Antigen Antigen Antigen Antibody ECD E-ΔCTE-Ala1 E-Ala2 Mf Antigen E 2968 6559 3454 14662 3388 29 2968G 2149 3759109 129 22 2969 2014 1857 7509 5671 3021 2969G 1347 610 6133 4942 25132970 5518 1324 14214 607 32 2970G 4683 599 12321 506 31 2971 501 4902506 2017 754 2971G 578 265 2457 2062 724 2972 2164 2158 8408 6409 31662972G 1730 992 6364 4602 2146 2973 3527 1148 3967 44 84 2973G 1294 2761603 28 44 2974 1766 722 8821 241 19 2974G 2036 228 8172 135 26 29751990 1476 8669 6134 2468 2975G 890 315 4194 3987 1376 2976 147 140 9961079 181 2976G 1365 460 6024 3929 1625

The anti-Antigen E common light chain antibody supernatants exhibitedhigh specific binding to the beads linked to Antigen E-ECD. For thesebeads, the negative control mock supernatant resulted in negligiblesignal (<10 MFI) when combined with the Antigen E-ECD bead sample,whereas the supernatants containing anti-Antigen E common light chainantibodies exhibited strong binding signal (average MFI of 2627 for 98antibody supernatants; MFI >500 for 91/98 antibody samples).

As a measure of the ability of the selected anti-Antigen E common lightchain antibodies to identify different epitopes on the ECD of Antigen E,the relative binding of the antibodies to the variants were determined.All four Antigen E variants were captured to the anti-myc Luminex™ beadsas described above for the native Antigen E-ECD binding studies, and therelative binding ratios (MFI_(variant)/MFI_(Antigen E-ECD)) weredetermined. For 98 tested common light chain antibody supernatants shownin Tables 11 and 12, the average ratios(MFI_(variant)/MFI_(Antigen E-ECD)) differed for each variant, likelyreflecting different capture amounts of proteins on the beads (averageratios of 0.61, 2.9, 2.0, and 1.0 for Antigen E-ACT, Antigen E-Ala1,Antigen E-Ala2, and Mf Antigen E, respectively). For each proteinvariant, the binding for a subset of the 98 tested common light chainantibodies showed greatly reduced binding, indicating sensitivity to themutation that characterized a given variant. For example, 19 of thecommon light chain antibody samples bound to the Mf Antigen E withMFI_(variant)/MFI_(Antigen E-ECD) of <8%. Since many in this groupinclude high or moderately high affinity antibodies (5 with K_(D)<5 nM,15 with K_(D)<50 nM), it is likely that the lower signal for this groupresults from sensitivity to the sequence (epitope) differences betweennative Antigen E-ECD and a given variant rather than from loweraffinities.

These data establish that the common light chain antibodies described inTables 3 and 4 indeed represent a diverse group of Antigen-E-specificcommon light chain antibodies that specifically recognize more than oneepitope on Antigen E.

What is claimed is:
 1. A mouse that expresses a population ofantigen-specific antibodies in response to challenge with an antigen,wherein all immunoglobulin light chains of the population ofantigen-specific antibodies comprise a human immunoglobulin light chainvariable (V_(L)) region derived from a single rearranged human lightchain variable region sequence in a germline of the mouse, wherein thesingle rearranged human light chain variable region sequence comprises ahuman germline Vκ1-39 gene segment and wherein immunoglobulin heavychains of the population comprise a human immunoglobulin heavy chainvariable (V_(H)) region cognate with said V_(L) region wherein the V_(H)region comprises a sequence derived from a human V_(H) segment selectedfrom V_(H)2-5, V_(H)3-23, V_(H)3-30, V_(H)4-59, and V_(H)5-51.
 2. Themouse of claim 1, wherein the single rearranged human light chainvariable region sequence further comprises a human germline Jκ5 genesegment.
 3. The mouse of claim 2, wherein the human germline Vκ1-39 genesegment is present in rearrangement with the human germline Jκ5 genesegment in the mouse germline.
 4. The mouse of claim 1, wherein themouse lacks a mouse immunoglobulin V_(L) and/or J_(L) segment(s).
 5. Themouse of claim 1, wherein the single rearranged human light chainvariable region sequence is operably linked to a murine immunoglobulinlight chain constant (C_(L)) region.
 6. The mouse of claim 1, whereinthe human V_(L) region is expressed from an endogenous mouseimmunoglobulin light chain locus.
 7. The mouse of claim 1, wherein thehuman V_(H) region further comprises a sequence derived from humanD_(H)6-6, D_(H)3-10, D_(H)3-3, D_(H)1-7, D_(H)5-12, D_(H)6-13,D_(H)7-27, D_(H)3-22, D_(H)3-16 or D_(H)5-5 gene segment.
 8. The mouseof claim 1, wherein the human V_(H) region further comprises a sequencederived from human J_(H)1, J_(H)3, J_(H)4, or J_(H)5 gene segment. 9.The mouse of claim 1, wherein the human V_(H) region is linked to amurine immunoglobulin heavy chain constant (C_(H)) region.
 10. The mouseof claim 1, wherein the human V_(H) region is expressed from anendogenous immunoglobulin heavy chain locus.
 11. A mouse that expressesa population of antigen-specific antibodies in response to challengewith an antigen, wherein all immunoglobulin light chains of thepopulation of antigen-specific antibodies comprise a humanimmunoglobulin light chain variable (V_(L)) region derived from a singlerearranged human light chain variable region sequence in the germline ofa mouse, wherein the single rearranged human light chain variable regionsequence comprises a human germline Vκ1-39 gene segment andimmunoglobulin heavy chains of the population comprise a humanimmunoglobulin heavy chain variable (V_(H)) region cognate with saidV_(L) region wherein the V_(H) region is derived from a humanV_(H)/D_(H)/J_(H) rearrangement selected from 2-5/6-6/1, 3-23/3-10/4,3-23/3-3/4, 3-30/6-6/1, 3-30/6-6/3, 3-30/1-7/4, 3-30/5-12/4,3-30/6-13/4, 3-30/6-6/4, 3-30/7-27/4, 3-30/3-22/5, 3-30/6-6/5,3-30/7-27/5, 4-59/3-16/3, 4-59/3-22/3, 4-59/3-16/4, and 5-51/5-5/3. 12.The mouse of claim 11, wherein the single rearranged human light chainvariable region sequence further comprises a human germline Jκ5 genesegment.
 13. The mouse of claim 12, wherein the human germline Vκ1-39gene segment is present in rearrangement with the human germline Jκ5gene segment in the mouse germline.
 14. The mouse of claim 11, whereinthe mouse lacks a mouse immunoglobulin V_(L) and/or J_(L) segment(s).15. The mouse of claim 11, wherein the single rearranged human lightchain variable region sequence is operably linked to a murineimmunoglobulin light chain constant (C_(L)) region.
 16. The mouse ofclaim 11, wherein the human V_(L) region is expressed from an endogenousmouse immunoglobulin light chain locus.
 17. The mouse of claim 11,wherein the human V_(H) region is linked to a murine immunoglobulinheavy chain constant (C_(H)) region.
 18. The mouse of claim 11, whereinthe human V_(H) region is expressed from an endogenous immunoglobulinheavy chain locus.
 19. A method of making an antibody comprising: (a)immunizing a genetically modified mouse with an antigen of interest,wherein the mouse comprises in its germline (i) an immunoglobulin κlight chain sequence that comprises a single rearranged human lightchain variable region sequence that comprises a human germline Vκ1-39gene segment, and (ii) at least one human V_(H), at least one humanD_(H), and at least one human J_(H) gene segment, wherein the at leastone human V_(H), D_(H), and J_(H) gene segments are at an endogenousmouse locus and are capable of rearranging to form a heavy chainvariable region sequence, wherein the heavy chain variable regionsequence is operably linked to a murine heavy chain constant sequence;(b) allowing the mouse to develop an immune response to the antigen ofinterest, wherein the mouse expresses a population of antibodies inresponse to the antigen of interest that comprise a human heavy chainvariable region (V_(H)) region derived from a human V_(H) segmentselected from V_(H)2-5, V_(H)3-23, V_(H)3-30, V_(H)4-59, and V_(H)5-51;(c) identifying a sequence that encodes a human V_(H) region thatspecifically binds to the antigen of interest; and (d) employing thesequence of (c) in making an antibody wherein the antibody comprises ahuman light chain variable region (V_(L)) derived from the singlerearranged human light chain variable region sequence and a human V_(H)region that is cognate with said V_(L) region.
 20. The method of claim19, wherein the single rearranged human light chain variable regionsequence further comprises a human germline Jκ5 gene segment, andwherein the human germline Vκ1-39 gene segment is present inrearrangement with the human germline Jκ5 gene segment in the mousegermline.
 21. The method of claim 19, wherein the mouse lacks a mouseimmunoglobulin V_(L) and/or J_(L) segment(s).
 22. The method of claim19, wherein the single rearranged human light chain variable regionsequence is operably linked to a murine immunoglobulin light chainconstant (C_(L)) region.
 23. The method of claim 19, wherein the humanV_(L) region is expressed from an endogenous mouse immunoglobulin lightchain locus.
 24. The method of claim 19, wherein the human V_(H) regionfurther comprises a sequence derived from human D_(H)6-6, D_(H)3-10,D_(H)3-3, D_(H)1-7, D_(H)5-12, D_(H)6-13, D_(H)7-27, D_(H)3-22,D_(H)3-16, or D_(H)5-5 gene segment.
 25. The method of claim 19, whereinthe human V_(H) region further comprises a sequence derived from humanJ_(H)1, J_(H)3, J_(H)4, or J_(H)5 gene segment.
 26. A mouse thatexpresses a population of antibodies wherein each immunoglobulin lightchain of the population comprises a human immunoglobulin light chainvariable (V_(L)) region derived from a single rearranged human lightchain variable region sequence in a germline of the mouse, wherein thesingle rearranged human light chain variable region sequence comprises ahuman germline Vκ3-20 gene segment or a human germline Vκ1-39 genesegment and wherein immunoglobulin heavy chains of the populationcomprise a human immunoglobulin heavy chain variable (V_(H)) regioncognate with said V_(L) region wherein the V_(H) region comprises asequence derived from human V_(H) segment 5-51.
 27. The mouse of claim26, wherein the single rearranged human light chain variable regionsequence further comprises a human germline Jκ1 or Jκ5 gene segment. 28.The mouse of claim 26, wherein the human V_(H) region further comprisesa sequence derived from a human J_(H)3, J_(H)5, or J_(H)6 gene segment.29. The mouse of claim 26, wherein the human V_(H) region furthercomprises a sequence derived from a human D_(H) 5-5, D_(H)3-16, orD_(H)6-13 gene segment.
 30. The mouse of claim 26 wherein the humanimmunoglobulin V_(H) region is derived from a human V_(H)/D_(H)/J_(H)gene segment rearrangement selected from 5-51/5-5/3, 5-51/6-13/5, or5-51/3-16/6.